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Expressions-with-variables/674338: A goes down river 9 miles, then back upriver for 3 miles. Rate of river current is 6 mph. How long does it take A to go the 12 miles? I have 9/x-6 for time downstream, and 3/x-6 for time upstream, but don't know how to set up the equation. (Answer is 1 hour.) 1 solutions
Answer 419167 by josmiceli(9686) on 2012-10-31 15:03:53 (Show Source):
You can put this solution on YOUR website!let  = A's rate in still water ( no current )
Going downstream, his rate is 
Going upstream, his rate is 
---------------
Going downstream,

Going upstream,

-------------------
You need to find

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

I think you're missing his rate in still water
Can't solve without it.
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percentage/674047: In June, Lindsey purchased an airfare ticket for $450 from Dallas to New York City. In July, the airline reduced the fare to $360. What percent is the reduction? (Please solve in percent decrease formula, i got 92% but im not sure i was absent yesterday and this is my make up work) 1 solutions
Answer 419013 by josmiceli(9686) on 2012-10-30 21:27:18 (Show Source):
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Travel_Word_Problems/673883: Two trains, one express and one local, leave Indianapolis at noon and head for Chicago 220 miles away. The express travels twice as fast as the local and arrives 2 hours ahead of the local. Find the speed of each train 1 solutions
Answer 418921 by josmiceli(9686) on 2012-10-30 16:46:07 (Show Source):
You can put this solution on YOUR website!Let  = the speed of the local train
Let  = the travel time for the local train
-----------
Equation for local train:
(1) 
Equation for express train:
(2) 
----------------------
(2) 
Substitute (1) into (2)
(2) 
(2) 
(2) 
(2)

The express train's speed is 110 m,i/hr
The local train's speed is 55 mi/hr
check answer:
(1) 
(1) 
(1) 
and
(2) 
(2) 
(2) 
OK
|
Square-cubic-other-roots/673723: I am really struggling when the 'power' is either a fraction, a decimal or a square root. For example 5^1.9 or 4^square root of 6.
5^1 would be 5^2 would be 25, so logic would tell me since 1.9 is slightly less than 2, the number would be less than the 25, but I have no idea how to work these. I know in the other example the square root of 6 is 2.44, so that should tell me that it would be equal to 4^2.44, but again, while 4^2 is 16, I think the answer would be greater than that, but do not know how to do the math! All help would be tremendously appreciated. I have gone back to school after a 35 year absence and math is giving me problems. 1 solutions
Answer 418849 by josmiceli(9686) on 2012-10-30 12:30:38 (Show Source):
You can put this solution on YOUR website!Basically, the answer is that you follow the
normal rules that you know when dealing
with whole numbers.
You are right that it's hard to get a feel for
what something like  means,
but all you can do is apply rules that you know, like
(1)  and
(2)  and
(3) 
---------------------
You can always convert decimals to fractions, too, if it helps
 , and using rule (1) backwards,

You could do this on a calculator that only has +,-,x, and square root
like the one I'm using
---------------------
If you have  , follow rule (3)

Note that  , so you have

The 1000th root of 3 is probably a little more than 1, so
the fraction 1/1.0+ should be a little less than 1
----------------------
Hope some of this helps
|
Average/673585: what is nCn. please i need help. my math teacher hates me!!!!!!!!!!!!!!!!!!!!!!!!!! 1 solutions
Answer 418723 by josmiceli(9686) on 2012-10-29 22:27:56 (Show Source):
You can put this solution on YOUR website!With combinations, you don't care about the order
of the things being counted.
Suppose
 is the combination of 10 things taken
10 at a time. There is only 1 of these, since you're
looking at all 10 of the things.The same is true no matter what  is
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Probability-and-statistics/673571: please help me!!!!
if 3 fair coins are tossed, find the probability of each number of heads.
1) 0
2) 2
3) 1 or 2 1 solutions
Answer 418722 by josmiceli(9686) on 2012-10-29 22:22:01 (Show Source):
You can put this solution on YOUR website!It helps if you write down all the possible outcome
H H H
T T T
H H T
H T H
T H H
T T H
T H T
H T T
There are 8 possible outcomes, which is 
(1)
no heads. Only T T T fits, so
P( 0H ) = 1/8
---------------
(2)
Exactly 2 heads. There are 3 of these, so
P( 2H ) = 3/8
---------------
(3)
Exactly 1 head or exactly 2 heads. When you see OR, you
add the separate probabilities
P( 1H ) = 3/8
P( 1H ) + P( 2H ) = 3/8 + 3/8
3/8 + 3/8 = 3/4
|
Rate-of-work-word-problems/673552: Justin starts at a point 26 miles from home and runs toward home at 6 mph. Rhonda starts from home 1.3 hours later and pedals toward Justin at 8 mph. How long has Justin been running when he meets Rhonda? How far from home do they meet? 1 solutions
Answer 418717 by josmiceli(9686) on 2012-10-29 22:04:31 (Show Source):
You can put this solution on YOUR website!Justin gets a head start of
 mi
They are then  mi apart
----------------
Let  = the distance Rhonda now has
to cover to meet Justin.
 = distance Justin now has to cover
Let  = the time it now takes them to meet
------------
After Justin's head start:
Justin's equation:
(1) 
Rhonda's equation:
(2) 
-------------
Substitute (2) into (1)
(1) 
(1) 
(1)  hrs
and
(1) 
(1) 
(1) 
(1) 
Justin has been running for  hrs
Rhonda travels  mi from home
where they meet
|
Travel_Word_Problems/673077: During the first 6 hours of a trip, you average 44 mi/h. During the last 4 hours of your trip, your average 50 mi/h. What is your average speed for the entire trip? 1 solutions
Answer 418476 by josmiceli(9686) on 2012-10-28 22:13:27 (Show Source):
You can put this solution on YOUR website!Average speed is always
( total distance ) / ( total time )
for 1st 6 hrs:
 mi
--------------
For the last 4 hrs:
 mi
--------------
The average speed is:
 mi/hr
|
Linear-equations/673083: What is x and y in this problem 3x +8y =101 1 solutions
Answer 418475 by josmiceli(9686) on 2012-10-28 22:06:52 (Show Source):
You can put this solution on YOUR website!It can't be solved
You need 1 equation if you have 1 unknown
You need 2 equations if you have 2 unknowns
You need 3 equations if you have 3 unknowns
You need 4 equations if you have 4 unknowns
You need 5 equations if you have 5 unknowns
etc.
|
Square-cubic-other-roots/673041: For some reason this still isn't clicking ....
homework problem finding the square root sets:
3(x+3)^2 = 36
Hellppp :( 1 solutions
Answer 418448 by josmiceli(9686) on 2012-10-28 20:58:41 (Show Source):
You can put this solution on YOUR website!
I can say

Take the square root of both sides
(1)

---------------------
Now go back to (1) and take the negative square root
of the right side
(1)

---------------------
You can plug both these results back into
the original problem
|
Rectangles/672940: The area is 4700 square feet. The length is twice the width minus six feet. I need help setting up the problem and solving it. 1 solutions
Answer 418409 by josmiceli(9686) on 2012-10-28 16:41:18 (Show Source):
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test/672830: Josh was in charge of bringing bags of chips to a homecoming party the doritos cost $1.79 per bag and the cheetos cost $2.01 per bag he bought 15 bags of chips together how many of each type did he buy if he spent a total of $28.17? 1 solutions
Answer 418334 by josmiceli(9686) on 2012-10-28 11:49:02 (Show Source):
You can put this solution on YOUR website!Let  = bags of Doritos bought
Let  = bags of Cheetos bought
given:
(1) 
(2) 
---------------------------
(2) 
Multiply both sides of (1) by 
and subtract (1) from (2)
(2) 
(1)

and
(1) 
(1) 
9 bags of Doritos were bought
6 bags of Cheetos were bought
check:
(2) 
(2) 
(2) 
OK
|
Travel_Word_Problems/672809: During rush hour, Fernando can drive 25 miles using the side roads in the same time that it takes to travel 20 miles on the freeway. If Fernando's rate on the side roads is 9 mi/h faster than his rate on the freeway, find his rate on the side roads? 1 solutions
Answer 418330 by josmiceli(9686) on 2012-10-28 11:31:02 (Show Source):
You can put this solution on YOUR website!Let  = his rate on the freeway
 = his rate on side roads
Let  = time for both
----------
On side roads:
(1) 
On freeway:
(2) 
---------------
(1) 
Substitute (2) into (1)
(1) 
(1) 
(1) 
--------------
On side roads:
(1) 
(1) 
(1) 
(1) 
(1)

His rate on side roads is 45 mi/hr
check:
(2) 
(2) 
(2)
|
Evaluation_Word_Problems/672812: The following formula models the number of prison inmates, P, in thousands who are in US prisons x years after 1980.
P=2x^2+20x+328
Find the first year in which the population of US prisons was approximately 440,000 people.
Thank you for your help 1 solutions
Answer 418321 by josmiceli(9686) on 2012-10-28 11:00:01 (Show Source):
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test/672714: 3{ [4 (x-1) +5] - [ 2 ( 2x-1) +5]}
i know "pemdas", but i cant figure this out. I dont get when to apply the distributive law, and how this cancles out. I guess the order us messing me up. 1 solutions
Answer 418269 by josmiceli(9686) on 2012-10-27 22:02:32 (Show Source):
You can put this solution on YOUR website!Always work from the inside out

One check that you can do is just count the
number of ( 's and the number of ) 's -they
should be the same. In this problem, they
both are 5.
------------
first step:

Now simplify:

The  doesn't really need to be in
parentheses at this point, also, do the
subtraction using distributive law.

Note that it doesn't matter what  is,
the result is still
|
Linear_Equations_And_Systems_Word_Problems/672706: Julio has found that his new car gets 36 miles per gallon on the highway
and 31 miles per gallon in the city. He recently drove 397 miles on 12
gallons of gasoline. How many miles did he drive on the highway? How
many miles did he drive in the city? 1 solutions
Answer 418266 by josmiceli(9686) on 2012-10-27 21:46:44 (Show Source):
You can put this solution on YOUR website!( miles/gallon ) x ( gallons used ) = miles driven
Let  = gallons used on highway
Let  = miles driven on highway
On highway:
(1) 
In city:
(2) 
---------------------------
(2) 
(2) 
Substitute (1) into (2)
(2) 
(2) 
(2)

and
(1) 
(1)

He drove 180 mi on the highway
he drove 217 mi in the city
-----------------------
check:
(2) 
(2) 
(2) 
(2) 
(2) 
OK
|
Rational-functions/672676: I am stumped.. when I solved the equation there was no need for the square root method. But that is what my hmwrk question is calling for. Will you please break this problem down for me so that I can see where I am messing up?
(x-3)^2 = 25 1 solutions
Answer 418255 by josmiceli(9686) on 2012-10-27 20:15:49 (Show Source):
You can put this solution on YOUR website!
Both sides are a perfect square
So you can take the square root of
both sides to simplify it.

Add  to both sides

------------
check the answer:

OK
|
test/672642: An oil tanker can be emptied by a main pump in 4hours an auxiliary pump can empty it in 9 hrs if the main pump is started at 9 am when should the auxiliary pump be started so the tanker will be empty by noon? 1 solutions
Answer 418244 by josmiceli(9686) on 2012-10-27 18:09:03 (Show Source):
You can put this solution on YOUR website!From 9 AM to noon is 3 hrs
Let  = number of hours the main pump
is used pumping by itself
 = number of hours that both pumps are pumping
---------------
The main pump's rate of pumping is ( 1 tanker / 4 hrs )
the auxilliary pump's rate is ( 1 tanker / 9 hrs )
----------------
( fraction of tanker pumped in x hrs ) +
( fraction pumped by both pumps in 3-x hrs ) = 1 whole tanker pumped
Multiply both sides by

The auxiliary pump should be started at 9:45
check answer:
In 3/4 of an hour the main pump empties
 of the tanker
In 2.25 hrs, both together empty

and 
OK
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Miscellaneous_Word_Problems/672531: A bell rings every 15 minutes . If the bell rang at 12:40, which of the following could be a time at which the bell had sounded? 1 solutions
Answer 418142 by josmiceli(9686) on 2012-10-27 09:28:14 (Show Source):
You can put this solution on YOUR website!15 minutes evenly divides 60 minutes, so the bell rings
happen at the same 4 minute mark every hour
12:40
12:55
1:10
1:25
1:40
------
So if the minutes is one of these, the
bell will ring no matter what the hour is
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Rectangles/672489: draw a square. show how you can double the area of this square and still keep it as a square. 1 solutions
Answer 418067 by josmiceli(9686) on 2012-10-26 23:55:53 (Show Source):
You can put this solution on YOUR website!Let the side of the square = 
Let  = the area of the square

note that what you are squaring is the diagonal
of the square, so just make another square
using the diagonal of the 1st square
|
Equations/672491: If I have the absolute value of x^2-9 is equal to 16, then what does "x" equal? 1 solutions
Answer 418066 by josmiceli(9686) on 2012-10-26 23:51:03 (Show Source):
You can put this solution on YOUR website!You don't have to worry about negative values
inside the absolute value because the expression
can never be more negative than 
So I can say

either value for  works
|
Money_Word_Problems/672468: An investment of 10,800 is deposited into two simple interest accounts. On one account the annual simple interest rate is 11.2%. On the other, the annual simple interest rate is 14%. How much should be invested in each account so that the interest earned is the same? 1 solutions
Answer 418062 by josmiceli(9686) on 2012-10-26 23:35:38 (Show Source):
You can put this solution on YOUR website!Let  = amount invested @ 11.2%
Let  = amount invested @ 14%
given:
(1) 
(2) 
-------------------
(2) 
(2) 
(2) 
Substitute this result into (1)
(1) 
(1) 
(1) 
and, since
(1) 
(1) 
(1) 
$6,000 should be invested @ 11.2%
$4,800 should be invested @ 14%
check:
(2) 
(2) 
(2) 
OK
|
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