Questions on Logic: Sets and operations answered by real tutors!

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Tutors Answer Your Questions about sets-and-operations (FREE)


Question 612378: I invested 50 000 more in teachers' cooperation than in home owners' cooperative. If my total investments in the two cooperatives is 110 000, how much is my investment in each?
Answer by bucky(2179) About Me  (Show Source):
You can put this solution on YOUR website!
Let x represent the unknown amount invested in the home owners' cooperative.
.
Since 50 000 more is invested in the teachers' cooperative, we can write that the investment in the teachers' cooperative is x + 50 000
,
The sum of these two investments is:
.
x + x + 50 000 and adding the two x terms results in a total of 2x + 50 000
.
But the problem tells you that the sum of the two investments is 110 000. Therefore, we can write the equation:
.
2x + 50 000 = 110 000
.
To solve this for x we can first eliminate the 50 000 on the left side by subtracting 50 000 from both sides to get:
.
2x = 60 000
.
Now we can solve for x by dividing both sides of this equation by 2 to get:
.
x = 30 000
.
Since we chose x to represent the amount invested in the home owners' cooperative, we know that we have 30 000 in it. And since 50 000 more was invested in the teachers' cooperative we know that we have invested 30 000 plus 50 000 for a total of 80 000 in the teachers cooperative.
.
And as a check, the total of 30 000 in the home owners' cooperative plus the 80 000 in the teachers' cooperative does add up to the total 110 000 that we have invested all together.
.
I hope this helps you to understand the problem and how you can solve it.
.


Question 612248: {q}∈{q,j,v,t,w} is this true or false?
Answer by stanbon(50471) About Me  (Show Source):
You can put this solution on YOUR website!
{q}∈{q,j,v,t,w} is this true or false?
----
false.
q is an element of {q,j,v,t,w}
but the set containing q is not.
----------------------------------
Cheers,
Stan H.


Question 606633: Given the sets:
vowels = {'a' ,'e', 'i', 'o', 'u'} and name = {'a', 'l', 'l, 'a', 'n'}
Which is FALSE?
- name ∪ vowels = {'a'}
- 'a' ∈ (vowels ∩ name)
- The cardinality of name = The cardinality of {'a', 'l', 'n' }
- The cardinality of vowels is equal to the cardinality of name
I would normally say it would be D in this case, as I think duplicate letters don't count such as name would be 3 and vowels would be 4.

Answer by jim_thompson5910(23765) About Me  (Show Source):
You can put this solution on YOUR website!
Choice A is false. So there must be a typo if there is only one possible answer. My guess is that the union symbol in choice A should be an intersection symbol.

If that's the case, then the answer is choice D.


Question 606645: Given the sets:
vowels = {'a' ,'e', 'i', 'o', 'u'} and name = {'a', 'l', 'l, 'a', 'n'}
Which is FALSE?
- name ∪ vowels = {'a'}
- 'a' ∈ (vowels ∩ name)
- The cardinality of name = The cardinality of {'a', 'l', 'n' }
- The cardinality of vowels is equal to the cardinality of name.
I would think it was D because the cardinality of vowels would be 5 and the cardinality of name would be 3, due to having more than one of the same letter.

Answer by Edwin McCravy(7327) About Me  (Show Source):
You can put this solution on YOUR website!
Given the sets:
vowels = {'a' ,'e', 'i', 'o', 'u'} and name = {'a', 'l', 'l, 'a', 'n'}
Which is FALSE?
- name ∪ vowels = {'a'}
That's false because (name ∪ vowels) = {'a', 'e', 'i', 'l', 'n', 'o','u'}

- 'a' ∈ (vowels ∩ name)
That's true because (vowels ∩ name) = {'a'} and 'a' ∈ {'a'}

- The cardinality of name = The cardinality of {'a', 'l', 'n' }
That's true because 'a', 'l', and 'n' are the only elements in the
set name, and that cardinality is 3.

- The cardinality of vowels is equal to the cardinality of name.
That's false because the cadinality of vowels is 5 and the cardinality
of names is only 3.


--------------------------

I would think it was D because the cardinality of vowels would be 5 and the cardinality of name would be 3, due to having more than one of the same letter
Yes, but the first one is also false.

Edwin


Question 597828: Let A = {5, 10, 15, 20} and B = {10, 20, 30}. What is the intersection of A and B?

Answer by jim_thompson5910(23765) About Me  (Show Source):
You can put this solution on YOUR website!
A intersect B = set of all things found in both sets A and B

A intersect B = {10, 20}



Question 597675: A set of data consists of the numbers 12, 20, 16, 31, 25, 22, 16, and 27. Which of thise measures would not change if 32 were added to the data set?
Answer by stanbon(50471) About Me  (Show Source):
You can put this solution on YOUR website!
A set of data consists of the numbers 12, 20, 16, 31, 25, 22, 16, and 27. Which of thise measures would not change if 32 were added to the data set?
---
The mode would still be 16.
Cheers,
Stan H.


Question 585750: 4-9+5*0+3=??
Found 2 solutions by mathhelp@, jim_thompson5910:
Answer by mathhelp@(10) About Me  (Show Source):
You can put this solution on YOUR website!
4-9+5*0+3=??
Let me explain easy :P
4-9 = -5
5*0 = 0
-5+0+3 = -2
your answer is -2

Answer by jim_thompson5910(23765) About Me  (Show Source):
You can put this solution on YOUR website!
4-9+5*0+3 = 4-9+0+3 = -2

So 4-9+5*0+3 = -2
--------------------------------------------------------------------------------------------------------------
If you need more help, email me at jim_thompson5910@hotmail.com

Also, please consider visiting my website: http://www.freewebs.com/jimthompson5910/home.html and making a donation. Thank you

Jim
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Question 572602: At the time of George W.Bush's presidency, there have been 43 presidents of the United States. Draw a Venn diagram showing the following facts about where each served before assuming the presidency. How many presidents served as vice-president and in the Senate, but did not serve in a cabinet post?
14 were vice-president.
6 served in the Senate.
15 held a cabinet post.
2 were VP and served in the Senate.
8 were VP and a held a cabinet post.
4 served in the Senate and held a cabinet post.
1 was VP, in the Senate, and held a cabinet post.

Answer by Latrice B(1) About Me  (Show Source):

Question 584187: Explain how to write this to set builder notation:
(-oo,5)U[8,oo)

Answer by jim_thompson5910(23765) About Me  (Show Source):
You can put this solution on YOUR website!
The set can be written as in set-builder notation.

The first part (-oo, 5) means that x < 5 while the second part (8, oo) means that x > 8. So we combine them together with an "or" to form the set shown above.
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If you need more help, email me at jim_thompson5910@hotmail.com

Also, please consider visiting my website: http://www.freewebs.com/jimthompson5910/home.html and making a donation. Thank you

Jim
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Question 584188: Explain how to write this in interval notation:
{x | -2 < x < 5}

Answer by jim_thompson5910(23765) About Me  (Show Source):
You can put this solution on YOUR website!
The set {x | -2 < x < 5} is written as in interval notation.

Notice how I used parenthesis to indicate that I'm excluding the endpoints.
--------------------------------------------------------------------------------------------------------------
If you need more help, email me at jim_thompson5910@hotmail.com

Also, please consider visiting my website: http://www.freewebs.com/jimthompson5910/home.html and making a donation. Thank you

Jim
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Question 585810: express in set builder notation: Z={13,14,15,16,17,18,19,20,21}
Answer by jim_thompson5910(23765) About Me  (Show Source):
You can put this solution on YOUR website!


This basically says that Z is the set of all x such that x is a natural number between 13 and 21.
--------------------------------------------------------------------------------------------------------------
If you need more help, email me at jim_thompson5910@hotmail.com

Also, please consider visiting my website: http://www.freewebs.com/jimthompson5910/home.html and making a donation. Thank you

Jim
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Question 584992: A palindrome is a positive integer that is the same when read forwards and backwards.For example, 545 and 1331 are both palindromes. The difference between the smallest three-digit palindrome and the largest three-digit palindrome is.....

I'm not very sure but they should be one of these A)909 B)898 C)888 D)979 E)878

Answer by ankor@dixie-net.com(13506) About Me  (Show Source):
You can put this solution on YOUR website!
The smallest would be 101 and the largest would be 999, right?
Diff would be 898


Question 572806: Is it true or false if the set A has three elements,then P(P(A)) )the power of the power set) has 32 elements??
Answer by solver91311(13359) About Me  (Show Source):
You can put this solution on YOUR website!


If is a finite set with elements, then the power set of contains elements. and

John

My calculator said it, I believe it, that settles it
The Out Campaign: Scarlet Letter of Atheism



Question 572111: I have been given a Venn Diagram. I am being asked to represent each set in roster form. How would I do this for a set such as A' Intersection symbol B?
Answer by nyc_function(2705) About Me  (Show Source):
You can put this solution on YOUR website!
I like faxing my answers to math questions. If you have a fax number, I will write my reply on paper and then fax the answer to you showing all the needed steps. If you need the answer right now, then please repost your question for others to see and reply.


Question 565018: You were assigned a locker for your books at school. You forgot the locker number but remmeber that two of the 12 positive factors of the locker number are 6 and 25. What is your locker number? Show or explain how you got your answer.
Answer by KMST(893) About Me  (Show Source):
You can put this solution on YOUR website!
If two of the positive factors of the number are
6=2%2A3 and 25=5%5E2 ,
the number must be a multiple of 2%2A3%2A5%5E2=150
The number 150 has 2%2A2%2A3=12 positive factors.
Any other number who has 6 and 25 as factors will be a multiple of 150, and will have more than 12 factors.
So your locker is number 150.
How do I know 2%2A3%2A5%5E2=150 has 2%2A2%2A3=12 positive factors?
Because all the factors will be of the form
2%5Ea%2A3%5Eb%2A5%5Ec where a and b could be 0 or 1, and c could be 0, 1, or 2.
That gives you 2 choices for a, 2 choices for b,and 3 choices for c. That makes 2%2A2%2A3=12 combinations.
In case you don't believe, I'll list the factors of 150
1=1%2A1%2A1=2%5E0%2A3%5E0%2A5%5E0 2=2%2A1%2A1=2%5E1%2A3%5E0%2A5%5E0
3=1%2A3%2A1=2%5E0%2A3%5E1%2A5%5E0 6=2%2A3%2A1=2%5E1%2A3%5E1%2A5%5E0
5=1%2A1%2A5=2%5E0%2A3%5E0%2A5%5E1 10=2%2A1%2A5=2%5E1%2A3%5E0%2A5%5E1
15=1%2A3%2A5=2%5E0%2A3%5E1%2A5%5E1 30=2%2A3%2A5=2%5E1%2A3%5E1%2A5%5E1
25=1%2A1%2A25=2%5E0%2A3%5E0%2A5%5E2 50=2%2A1%2A25=2%5E1%2A3%5E0%2A5%5E2
75=1%2A3%2A25=2%5E0%2A3%5E1%2A5%5E2 150=2%2A3%2A25=2%5E1%2A3%5E1%2A5%5E2


Question 562097: what is 10t-3=t+15
Answer by Alan3354(23885) About Me  (Show Source):
You can put this solution on YOUR website!
what is 10t-3=t+15
----------
It's an equation in t


Question 561295: Numeration System and Sets
Explain how you would decide how to divide a school of 2080 students into sets?
50-100 words
thanks for all help
really makes a difference

Answer by jim_thompson5910(23765) About Me  (Show Source):
You can put this solution on YOUR website!
You can divide them up by class, gender, height, age, social circle, etc to form many sets. For example, you could have one set be the set of all boys and the other be the set of all girls.


Question 558277: 1722.21 is 4.2 % of what number?
Answer by bluemockingjay7(41) About Me  (Show Source):

Question 557271: Express the set in roster form. c = {x|x+3=44}
Answer by stanbon(50471) About Me  (Show Source):
You can put this solution on YOUR website!
Express the set in roster form.
c = {x|x+3=44}
----
Since x+3 = 44 implies that x = 41,
---
c = {41}
===============
Cheers,
Stan H.


Question 551065: In a certain party each one of the group drinks coke or beer or whiskey or all. also 400 drink coke, 500 drink beer and 300 drink whiskey. 100 drink coke and beer, 200 drink beer and whiskey. 1 who drinks whiskey does not drink coke. how many are in the group?
Answer by Edwin McCravy(7327) About Me  (Show Source):
You can put this solution on YOUR website!
In a certain party each one of the group drinks coke or beer or whiskey or all. also 400 drink coke, 500 drink beer and 300 drink whiskey. 100 drink coke and beer, 200 drink beer and whiskey. 1 who drinks whiskey does not drink coke. how many are in the group?
 
drawing%28500%2C500%2C-4%2C4%2C-5%2C4%2C%0D%0A+%0D%0Acircle%280%2C-.5%2C2%29%2C%0D%0Alocate%28-2%2C2%2Cd%29%2C%0D%0A+%0D%0Alocate%280%2C-2.7%2CW%29%2C%0D%0Alocate%28-.3%2C-1%2Cj%29%2C%0D%0Alocate%281.1%2C.4%2Ci%29%2C%0D%0Acircle%28sqrt%282%29%2Csqrt%282%29%2C2%29%2C%0D%0Alocate%28-3.5%2C2.5%2CC%29%2C%0D%0Acircle%28-sqrt%282%29%2Csqrt%282%29%2C2%29%2C%0D%0Alocate%283.5%2C2.5%2CB%29%2C%0D%0Alocate%28-1.3%2C.5%2Cg%29%2C%0D%0Alocate%280%2C2.5%2Ce%29%2C%0D%0Alocate%282%2C2%2Cf%29%2C%0D%0Alocate%28-.2%2C1.1%2Ch%29+%29
 
There are 7 regions in the Venn diagram above
Circle C contains all the Coke drinkers, which are of 4 types:
Circle C is made up of 4 regions d,e,f, and h
Those in region d drink Coke but do not drink beer or whiskey
Those in region e drink Coke and beer, but do not drink whiskey.
Those in region h drink Coke, beer, and whiskey.
Those in region g drink Coke and whiskey, but do not drink beer.
 
Circle B contains all the beer drinkers, which are of 4 types:
Circle B is made up of 4 regions e,f,h, and i
Those in region e drink beer and Coke, but do not drink whiskey.
Those in region f drink beer, but do not drink coke or whiskey.
Those in region h drink beer, Coke, and whiskey.
Those in region i drink beer and whiskey, but do not drink Coke.
 
Circle W contains all the whiskey drinkers, which are of 4 types:
Circle W is made up of 4 regions g,h,i, and j
Those in region g drink whishey and Coke, but do not drink beer.
Those in region h drink whiskey, Coke, and beer.
Those in region i drink whiskey and beer, but do not drink Coke.
Those in region j drink whiskey, but do not drink Coke or beer.
 
Let's start with this clue:

>>...1 who drinks whiskey does not drink Coke. how many are in the group?

I take this to mean nobody drinks both Coke and whiskey.  That
means there are nobody in regions g and h.  So we put 0's there



drawing%28500%2C500%2C-4%2C4%2C-5%2C4%2C%0D%0A+%0D%0Acircle%280%2C-.5%2C2%29%2C%0D%0Alocate%28-2%2C2%2Cd%29%2C%0D%0A+%0D%0Alocate%280%2C-2.7%2CW%29%2C%0D%0Alocate%28-.3%2C-1%2Cj%29%2C%0D%0Alocate%281.1%2C.4%2Ci%29%2C%0D%0Acircle%28sqrt%282%29%2Csqrt%282%29%2C2%29%2C%0D%0Alocate%28-3.5%2C2.5%2CC%29%2C%0D%0Acircle%28-sqrt%282%29%2Csqrt%282%29%2C2%29%2C%0D%0Alocate%283.5%2C2.5%2CB%29%2C%0D%0Alocate%28-1.3%2C.5%2C0%29%2C%0D%0Alocate%280%2C2.5%2Ce%29%2C%0D%0Alocate%282%2C2%2Cf%29%2C%0D%0Alocate%28-.2%2C1.1%2C0%29+%29



>>...100 drink coke and beer...<<
 
So all 100 go in e since there are 0 in the middle. So we replace
e by 100

drawing%28500%2C500%2C-4%2C4%2C-5%2C4%2C%0D%0A+%0D%0Acircle%280%2C-.5%2C2%29%2C%0D%0Alocate%28-2%2C2%2Cd%29%2C%0D%0A+%0D%0Alocate%280%2C-2.7%2CW%29%2C%0D%0Alocate%28-.3%2C-1%2Cj%29%2C%0D%0Alocate%281.1%2C.4%2Ci%29%2C%0D%0Acircle%28sqrt%282%29%2Csqrt%282%29%2C2%29%2C%0D%0Alocate%28-3.5%2C2.5%2CC%29%2C%0D%0Acircle%28-sqrt%282%29%2Csqrt%282%29%2C2%29%2C%0D%0Alocate%283.5%2C2.5%2CB%29%2C%0D%0Alocate%28-1.3%2C.5%2C0%29%2C%0D%0Alocate%28-.1%2C2.5%2C100%29%2C%0D%0Alocate%282%2C2%2Cf%29%2C%0D%0Alocate%28-.2%2C1.1%2C0%29+%29

>>...200 drink beer and whiskey...<<

So all 200 go in i since there are 0 in the middle. So we replace
i by 200

drawing%28500%2C500%2C-4%2C4%2C-5%2C4%2C%0D%0A+%0D%0Acircle%280%2C-.5%2C2%29%2C%0D%0Alocate%28-2%2C2%2Cd%29%2C%0D%0A+%0D%0Alocate%280%2C-2.7%2CW%29%2C%0D%0Alocate%28-.3%2C-1%2Cj%29%2C%0D%0Alocate%281.1%2C.4%2C200%29%2C%0D%0Acircle%28sqrt%282%29%2Csqrt%282%29%2C2%29%2C%0D%0Alocate%28-3.5%2C2.5%2CC%29%2C%0D%0Acircle%28-sqrt%282%29%2Csqrt%282%29%2C2%29%2C%0D%0Alocate%283.5%2C2.5%2CB%29%2C%0D%0Alocate%28-1.3%2C.5%2C0%29%2C%0D%0Alocate%28-.1%2C2.5%2C100%29%2C%0D%0Alocate%282%2C2%2Cf%29%2C%0D%0Alocate%28-.2%2C1.1%2C0%29+%29

>>...400 drink coke...<<

Three of the regions of circle C have 100, 0 and 0 in them.
So we have already accounted for 100 of the Coke-drinkers,
so the remaining 300 coke-drinkers are in region d.  So we
replace d by 300:

drawing%28500%2C500%2C-4%2C4%2C-5%2C4%2C%0D%0A+%0D%0Acircle%280%2C-.5%2C2%29%2C%0D%0Alocate%28-2%2C2%2C300%29%2C%0D%0A+%0D%0Alocate%280%2C-2.7%2CW%29%2C%0D%0Alocate%28-.3%2C-1%2Cj%29%2C%0D%0Alocate%281.1%2C.4%2C200%29%2C%0D%0Acircle%28sqrt%282%29%2Csqrt%282%29%2C2%29%2C%0D%0Alocate%28-3.5%2C2.5%2CC%29%2C%0D%0Acircle%28-sqrt%282%29%2Csqrt%282%29%2C2%29%2C%0D%0Alocate%283.5%2C2.5%2CB%29%2C%0D%0Alocate%28-1.3%2C.5%2C0%29%2C%0D%0Alocate%28-.1%2C2.5%2C100%29%2C%0D%0Alocate%282%2C2%2Cf%29%2C%0D%0Alocate%28-.2%2C1.1%2C0%29+%29

>>...500 drink beer...<<

Three of the regions of circle B have 100, 0 and 200 in them.
So we have already accounted for 300 of the beer-drinkers,
so the remaining 200 beer-drinkers are in region f.  So we
replace f by 200:

drawing%28500%2C500%2C-4%2C4%2C-5%2C4%2C%0D%0A+%0D%0Acircle%280%2C-.5%2C2%29%2C%0D%0Alocate%28-2%2C2%2C300%29%2C%0D%0A+%0D%0Alocate%280%2C-2.7%2CW%29%2C%0D%0Alocate%28-.3%2C-1%2Cj%29%2C%0D%0Alocate%281.1%2C.4%2C200%29%2C%0D%0Acircle%28sqrt%282%29%2Csqrt%282%29%2C2%29%2C%0D%0Alocate%28-3.5%2C2.5%2CC%29%2C%0D%0Acircle%28-sqrt%282%29%2Csqrt%282%29%2C2%29%2C%0D%0Alocate%283.5%2C2.5%2CB%29%2C%0D%0Alocate%28-1.3%2C.5%2C0%29%2C%0D%0Alocate%28-.1%2C2.5%2C100%29%2C%0D%0Alocate%282%2C2%2C200%29%2C%0D%0Alocate%28-.2%2C1.1%2C0%29+%29
 
>>...300 drink whiskey...<<

Three of the regions of circle W have 0, 0 and 200 in them.
So we have already accounted for 200 of the whiskey-drinkers,
so the remaining 100 whiskey-drinkers are in region j.  So we
replace j by 100:

drawing%28500%2C500%2C-4%2C4%2C-5%2C4%2C%0D%0A+%0D%0Acircle%280%2C-.5%2C2%29%2C%0D%0Alocate%28-2%2C2%2C300%29%2C%0D%0A+%0D%0Alocate%280%2C-2.7%2CW%29%2C%0D%0Alocate%28-.3%2C-1%2C100%29%2C%0D%0Alocate%281.1%2C.4%2C200%29%2C%0D%0Acircle%28sqrt%282%29%2Csqrt%282%29%2C2%29%2C%0D%0Alocate%28-3.5%2C2.5%2CC%29%2C%0D%0Acircle%28-sqrt%282%29%2Csqrt%282%29%2C2%29%2C%0D%0Alocate%283.5%2C2.5%2CB%29%2C%0D%0Alocate%28-1.3%2C.5%2C0%29%2C%0D%0Alocate%28-.1%2C2.5%2C100%29%2C%0D%0Alocate%282%2C2%2C200%29%2C%0D%0Alocate%28-.2%2C1.1%2C0%29+%29

Now we have all 7 regions filled with numbers, so
we add them up:

300+100+200+0+0+200+100 = 900

So there were 900 at the party.  What a party!

Edwin


Question 478455: Use an Euler diagram to determine whether the syllogism is valid or invalid.
1.
All Cats have whiskers.
All things with whiskers are dogs.
[symbol] All cats are dogs.

Answer by nanpost1(1) About Me  (Show Source):

Question 549953: solve x=|1/2| + |-5/2|
Answer by josmiceli(7367) About Me  (Show Source):

Question 549952: given the universal set E={1,2,3,4,5,6,7,8,9,10}
what is the complement of {1,10}

Answer by richard1234(5244) About Me  (Show Source):
You can put this solution on YOUR website!
{2,3,4,5,6,7,8,9}


Question 549654: find f(g(x) and g(f(x)
a) f(x)= -3x ,g(x)=2x+6
b) f(x)= x^2 + 4x , g(x)= x-1

Answer by mathie123(224) About Me  (Show Source):
You can put this solution on YOUR website!
a) f(x)= -3x ,g(x)=2x+6

f(g(x)) is just basically saying everywhere you have an x in f(x), put the entire g(x) function.
So for this example, f(g(x))=-3(2x+6)
and g(f(x)) is just saying everywhere you have and x in g(x), put the entire f(x) function
So for this example, g(f(x))=2(-3x)+6
I will let you do b) yourself (hint: VERY similar to a), just different functions.

_____________________________________________________________________
Hopefully this helps! Let me know if you are still unsure
Romans 5:8


Question 517801: Could you express the following set in set-builder notation?
B={4,5,6,7,8,9,10,11}

Answer by solver91311(13359) About Me  (Show Source):
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John

My calculator said it, I believe it, that settles it
The Out Campaign: Scarlet Letter of Atheism



Question 517668: A={3x: x ∈ N}
B={x+7: x ∈ N)
C={3x+21: x∈ N)
Prove AnB⊆C and C⊆AnB. (n=intersect). If false explain why it does not hold.

Answer by Gogonati(778) About Me  (Show Source):
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A≴B, A∐B, A∎B, x∌y, x∉y, x∈y, x∇y
x∆y, x∅y, xℹy, x↢y, x≪y, x≥y, x≦y
x≧y, x≨y, x≩y, x≪y, x≫y, x≬y, x≭y
x≡y, x≢y, x≣y, x≤y, x⇼y, x∁y, x⇿y
xy, xϩy, xߑy, xಌy, xᇊy, xᎉy, xᖩy
x᪔y, xṽy, xṺy, xṼy, xṾy, xṿy, xờy
xὁy, xᾩy, x y, x‍y, a‍b, x‎y, xy
x∃y, x∂y, x∄y, x∅y, x∈y, x∉y, x∊y
x∋y, x∌y, x∍y, x∎y, x∏y, x∐y, x∑y
∑B


Question 515089: Hello, I am having trouble with this problem
Find the N(A) for the set
700,701,702,.....,7000

Answer by richard1234(5244) About Me  (Show Source):
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Subtract 699 from each element (this does not change the cardinality of the set).

1,2,3,...,6301

Hence the cardinality, or n(A), is 6301.


Question 511628: one number is 3 times another number. Find the numbers if the sum of their reciprocal is 1.
Found 2 solutions by josmiceli, oberobic:
Answer by josmiceli(7367) About Me  (Show Source):
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+a+=+3b+
+1%2Fa+%2B+1%2Fb+=+1+
+1%2F%283b%29+%2B+1%2Fb+=+1+
Multiply both sides by +3b+
+1+%2B+3+=+3b+
+3b+=+4+
+b+=+4%2F3+
and,
+a+=+3b+
+a+=+4+
The numbers are 4/3 and 4
check:
+1%2Fa+%2B+1%2Fb+=+1+
+1%2F4+%2B+1%2F%284%2F3%29+=+1+
+1%2F4+%2B+3%2F4+=+1+
OK

Answer by oberobic(2303) About Me  (Show Source):
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1%2Fx+%2B+1%2Fy+=+1
.
x+=+3y
.
1%2F%283y%29+%2B+1%2Fy+=+1
.
Multiply through by 3y
.
1+%2B+3+=+3y
.
3y+=+4
.
y+=+4%2F3
.
x+=+3%2A%284%2F3%29+=+3%2A4%2F3+=+4
.
Check the sum of reciprocals.
.
1%2F4+%2B+3%2F4+=+1
Correct.
.
Answer: One number is 4/3 and the other is 4.
.
Done.


Question 510299: There are a total of 108 foreign language students in a high school where they offer Spanish, French, and German.
There are 21 students who take at least 2 languages at once.
If there are
44 students of Spanish,
45 students of French, and
40 students of German,
how many students take all three languages at once?

Answer by edjones(7481) About Me  (Show Source):
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Let 21 take spanish and french.
Then 44-21=23 take only spanish.
45-21=24 take only french.
40 take only German.
21+23+24+40=108
None take all 3 languages.
.
Ed


Question 500817: 1. Whenever we encounter a new proposition, it is a good idea to explore the
proposition by looking at specific examples. For example, let
a =20, b = 12, and t = 4. In this case, t given a and t given b. In each of
the following cases, determine the value of (ax + by) and determine if t
divides (ax + by).
(a) x = 1; y = 1 a. yes
(b) x = 1; y = -1 b. yes
(c) x = 2; y = 2 c. yes
(d) x = 2; y= -3 d. yes
(e) x = -2; y = 3 e. yes
(f) x = -2; y = -5 f. yes
2. Repeat Part (1) with a = 21, b = -6, and t =3.
a. yes d. yes
b. yes e. yes
c. yes f. yes
3. We started the forward-backward process for the proof of Proposition 4.15
following the discussion of this proposition. Complete the following proof
of Proposition 4.15.
Proposition 4.15. Let a, b, and t be integers with t ≠ 0. If t divides a and t
divides b, then for all integers x and y, t divides ax + by.
Proof. Let a, b, and t be integers with t ≠ 0, and assume that t divides a and
t divides b. We will prove that for all integers x and y, t divides (ax + by).
So let x is an element of Z and let y is an element of Z. Since t divides a, there exists an integer m such that ….

Answer by richard1234(5244) About Me  (Show Source):
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Pretty straightforward. If t divides a and t divides b, then a ≡ 0 (mod t) and b ≡ 0 (mod t). Then we can multiply a and b by integers and the residue is still 0 mod t (i.e. ax ≡ 0, by ≡ 0). Then we can add them and we obtain our desired result, ax + by ≡ 0 (mod t) <--> t divides ax + by.


Question 500690: One of the most famous unsolved problems in mathematics is a conjecture
made by Christian Goldbach in a letter to Leonhard Euler in 1742. The
conjecture made in this letter is now known as Goldbach’s Conjecture. The
conjecture is as follows:
Every even integer greater than 2 can be expressed as the sum of two
(not necessarily distinct) prime numbers.
Currently, it is not known if this conjecture is true or false, although most
mathematicians believe it to be true.
(a) Describe one way to prove that Goldbach’s Conjecture is false.
(b) Prove the following:
If there exists an odd integer greater than 5 that is not the sum of
three prime numbers, then Goldbach’s Conjecture is false.

Answer by solver91311(13359) About Me  (Show Source):
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1. Find an even integer greater than 2 that cannot be expressed as the sum of two prime numbers.

2. Let be an odd integer greater than 5 such that three not necessarily distinct prime numbers that sum to do not exist. Let be a prime number greater than 2, then must be odd. The difference of any two odd integers is even . Hence, is even. But Goldberg's conjecture says that must be the sum of two primes, and therefore must be the sum of three primes. Therefore, if exists, there must be a that is even and not the sum of two primes proving Goldberg's Conjecture false.


John

My calculator said it, I believe it, that settles it
The Out Campaign: Scarlet Letter of Atheism



Question 495875: It was stated that a real function is a function whose domain
and codomain are subsets of the real numbers R. Most of the functions
used in calculus are real functions. Quite often, a real function is given by a
formula or a graph with no specific reference to the domain or the codomain.
In these cases, the usual convention is to assume that the domain of the real
function f is the set of all real numbers x for which f(x) is a real number and that the codomain is R. For example, if we define the (real) function f
by,
f(x)=x/x-2,
we would be assuming that the domain is the set of all real numbers that are not equal to 2.
Determine the domain and range of each of he following real functions.
a.)The function k defined by k(x)=the square root x-3
b.)The function F defined by F(x)=In(2x-1)
c.)The function f defined by f(x)=3 sin(2x)
d.)The function g defined by g(x)=4/x^2 - 4

Answer by richard1234(5244) About Me  (Show Source):
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Simply find the set of all possible x-values, and the set of all possible y-values. For example,



is not defined on real numbers if x < 3. Also, the range of k(x) is [0, infinity) because the square root of any real number is nonnegative.

Try the others the same way.


Question 490329: Find a counterexample to show that the following statement is false:
The sum of twi-digit numbers is a three-digit number.
__ + __ is a two-digit number.

Answer by Alan3354(23885) About Me  (Show Source):
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11 + 12 = 23
---------------
36 + 55 = 91
etc


Question 489859: How would you write the following set using set builder notation: B={3,7,11,15,19}.
Answer by stanbon(50471) About Me  (Show Source):
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How would you write the following set using set builder notation: B={3,7,11,15,19}.
-----------
B = {3 + 4x| x = 0,1,2,3.4}
============================
Cheers,
Stan H.


Question 484526: I'm having a problem with this set. The question is..
Prior to the 7:15 show at the local movie theater, 70 people visited the concession stand, Listed below is what they ordered
42 ordered popcorn
18 ordered candy
30 ordered a soda
10 ordered popcorn and candy
8 ordered soda and candy
12 ordered popcorn and soda
5 ordered popcorn, candy and soda
1. How many people ordered something other than popcorn, candy or soda?
2. How many people ordered popcorn and a soda but not candy?
3. How many people ordered candy or a soda but not popcorn?
4. How many people ordered popcorn or candy?

Answer by solver91311(13359) About Me  (Show Source):
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Draw a large rectangle. Inside of the rectangle draw three circles that partially overlap.

Label the circles P, C, and S.

In the very center where the three circles overlap, that is to say the one region on your diagram where you are inside of all three circles, put the number 5 representing the 5 people who ordered P, C, AND S.

The region where P and C overlap needs to contain the number of people who ordered ONLY P and C. The number 10 given for people who ordered P and C also includes those who ordered P, C, and S. So from the given 10 subtract those that ordered all three, that is 10 minus 5 = 5. And you put 5 into the P and C only region. Similarly, since 12 minus 5 equals 7, you put 7 in the P & S only region. Then, since the number who ordered P includes those who ordered P & C, those who ordered P & S, AND those who ordered all three, add up 5 plus 7 plus 5 = 17, then subtract 17 from the 42 we are told ordered P to arrive at 25 who ordered ONLY P. Use similar logic to fill in the rest of your diagram.

Next add all of the numbers that you have entered in your diagram. Subtract that result from 70, the number of people surveyed, to get the number of people who did not order P, S, OR C. Several of us only wanted ice cream. Write that number in the rectangle outside of all of the circles.

You should be able to answer all of the questions posed just from the data in your diagram.

John

My calculator said it, I believe it, that settles it
The Out Campaign: Scarlet Letter of Atheism



Question 482658: Problem says this, and it is a multiple choice question:
Given the following sets, select the statement below that is NOT true.
A = {b, l, a, z, e, r}
B = {b, a, l, e}
C = {a, b, l, e}
D = {l, a, b}
E = {a, b, l}
Multiple choice possibilities:
1. E ⊂ A
2. C ⊂ A
3. D ⊆ B
4. C ⊂ B
5. D ⊂ A
Could someone help me with this, please? Thank you.

Answer by Edwin McCravy(7327) About Me  (Show Source):
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Problem says this, and it is a multiple choice question:
Given the following sets, select the statement below that is NOT true.
A = {b, l, a, z, e, r} 
B = {b, a, l, e} 
C = {a, b, l, e} 
D = {l, a, b} 
E = {a, b, l} 

You need to learn the difference betweeen ⊂ and ⊆.

It's like the difference between < and ≤.  A line under either symbol
means "EQUALITY IS ALLOWED BUT NOT REQUIRED",  When there is no line
underneath, it means "EQUALITY IS NOT ALLOWED".


Multiple choice possibilities:
1. E ⊂ A, TRUE because "a,b,&l" are all part of but not all of "b,l,a,z,&e" 
2. C ⊂ A, TRUE because "a,b,l,&e" are all part of but not all of "b,l,a,z,&e  
3. D ⊆ B, TRUE because "l,a,&b" is part of or all of "b,a,l,&e".  
4. C ⊂ B, FALSE because "a,b,l,&e" is ALL OF, not just part of "b,a,l,&e"
5. D ⊂ A, TRUE because "l,a,&b" are all part of but not all of "b,l,a,z,&e" 

Edwin


Question 482196: The problem says this:
Are the two sets equal, equivalent, neither or both?
V = {eye, nose, ear, mouth, tongue}; W = {tongue, ear, mouth, eye, nose}
Will someone help me with this? Also, to get a better understanding of this, would you mind explaining your answer? Thank you so much!

Found 2 solutions by MathLover1, stanbon:
Answer by MathLover1(3383) About Me  (Show Source):
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They are both equal and equivalent.
Rearranging the elements in a different order between the braces does not change the set.

by definition:
Two sets are equivalent if their cardinality is equal.
The cardinality of a set is the number of elements in the set.
The cardinality of V is 5 and the
The cardinality of W is 5. So the sets are equivalent.
Two sets are equal if the two sets consist of the exact same elements.
Set W and set V have the same elements.

Answer by stanbon(50471) About Me  (Show Source):
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Are the two sets equal, equivalent, neither or both?
V = {eye, nose, ear, mouth, tongue}; W = {tongue, ear, mouth, eye, nose}
---
V and W are equal.
They have the same elements: no more and no less.
----
Equivalent sets have the same number of elements
but not the same elements.
---
Cheers,
Stan H.


Question 482202: Problem says this:
Given
U = {15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25}
A = {16, 18, 20, 22}
B = {17, 19, 20, 23, 24}
Find A′∩ B′.
Could you please help me with this? Thank you so much!

Answer by stanbon(50471) About Me  (Show Source):
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U = {15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25}
A = {16, 18, 20, 22}
B = {17, 19, 20, 23, 24}
Find A′∩ B′.
----
A' = {15,17,19,21,23,24,25}
B' = {15,16,18,21,22,25}
----
A' AND B' = {15,21,25}
=========================
Cheers,
Stan H.
================


Question 482194: Problem says:
Express the following in roster form: Set M is the set of natural numbers between seventeen and twenty-three.
Could someone help me with this, please? Thank you so much.

Answer by stanbon(50471) About Me  (Show Source):
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Express the following in roster form: Set M is the set of natural numbers between seventeen and twenty-three.
-------------------------
M = {18,19,20,21,22}
================
Cheers,
Stan H.


Question 481414: The problem says this:
Find P ∩ Q. Write in correct set notation.
The diagram:
http://www.flickr.com/photos/62474130@N03/6040495154/
Could you help me with please? Thank you.

Answer by mananth(11019) About Me  (Show Source):
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(P ∩ Q) ={i,s}


Question 481352: The problem says this, and it is multiple choice:
Given the following sets, select the statement below that is true.
A = {b, l, a, z, e, r}, B = {b, a, l, e}, C = {a, b, l, e}, D = {l, a, b}, E = {l, a}
1. E ⊆ A and B ⊂ C
2. C ⊂ D and E ⊂ C
3. D ⊆ C and D ⊆ E
4. C ⊂ E and B ⊆ A
5. D ⊂ C and B ⊆ C
Can you help me with this please? Thank you so much!



Answer by Theo(3065) About Me  (Show Source):
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⊆ means improper subset
⊂ means proper subset
an improper subset means that A is a subset of B, but B doesn't contain any elements in it other than the elements that are also in A.
an example would be:
A = {a,b,c,d}
B = {a,b,c,d}
these sets are identical so:
A ⊆ B and B ⊆ A are valid.
a proper subset means that A is a subset of B, but B contains additional elements that are not in A.
an example would be:
A = {a,b,c}
B = {a,b,c,d}
A ⊂ B is valid.
B ⊂ A is not valid.
All elememnts in A are in B, but B contains additional elements not in A, namely d.
here's a reference from the web that explains it as well.
http://answers.yahoo.com/question/index?qid=20080125081016AA94Fwe
i analyzed each of your statements in turn and found the following:
1. E ⊆ A and B ⊂ C
     E is a proper subset of A because it has less elements than A.
     B is an improper subset of C because they both contain the same elements.
     This answer is not correct.
2. C ⊂ D and E ⊂ C
     C cannot be a subset of D because D contains fewer elements than C.
     if anything, it would be the other way around.
     D ⊂ C would be more appropriate.
3. D ⊆ C and D ⊆ E
     D is a proper subset of C, not an improper subset.
     Also D is not a subset of E because E contains fewer elements than D.
4. C ⊂ E and B ⊆ A
     C is not a subset of E because E contains fewer elements than C.
5. D ⊂ C and B ⊆ C
     D is a proper subset of C because D contains fewer elements than C.
     B is an improper subset of C because they both contain the same elements.
     THIS ONE LOOKS CORRECT !!!!!

I believe your answer is selection 5.
D contains {b,l,a}
C contains {b,l,a,e}
B contains {b,l,a,e}
it does help to reorder the terms so you can see the relationships easier.
you can see that B and C are identical sets, so B ⊆ C is correct.
you can see that all elements in D are also in C and that D contains fewer elements than C, so D ⊂ C is correct.
I'd go with selection 5.





Question 481009: Can someone help me with this please?
My Problem says this:
Determine the following: A ∪ B′
Let
U = {1, 2, 3, 4, 5, 6, 7, 8}
A = {1, 2, 4, 5, 8}
B = {2, 3, 4, 6}
The photo:
http://www.flickr.com/photos/62474130@N03/6036660666/

Answer by solver91311(13359) About Me  (Show Source):
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B' is everything that is in U but not in B. A ∪ B' is everything that is either in A, in B', or in both.

John

My calculator said it, I believe it, that settles it
The Out Campaign: Scarlet Letter of Atheism




Older solutions: 1..45, 46..90, 91..135, 136..180, 181..225