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Word_Problems_With_Coins/257726: How many ways can you make $0.25 using pennies, nickels, dimes, and quarters

1 solutions

Answer 189597 by drk(1908) About Me  on 2010-01-17 15:07:39 (Show Source):
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There appear to be 13 ways. Here they are in {p,n,d,q} form:
{p,n,d,q}
{0,0,0,1}
(0,1,2,0}
{5,0,2,0}
{0,3,1,0}
{5,2,1,0}
{10,1,1,0}
{15,0,1,0}
{0,5,0,0}
{5,4,0,0}
{10,3,0,0}
{15,2,0,0}
{20,1,0,0}
{25,0,0,0}


Functions/257728: Find the function value.
F(x) = x to the third power.
F(-9) =
1 solutions

Answer 189596 by drk(1908) About Me  on 2010-01-17 15:02:16 (Show Source):
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F(x) = x^3
F(-9) = (-9)^3 = -9*-9*-9 = -729


Linear-equations/257732: how do I solve k(x)=x+20
k (o)=
k(-17)=
k (-12)=
k(14)=
K (d+17)=
1 solutions

Answer 189595 by drk(1908) About Me  on 2010-01-17 15:00:45 (Show Source):
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To solve these, use the phrase "letter goes away and number comes to stay as follows:
k(x)=x+20
k(0) = 0 + 20 = 20
k(-17) = -17 + 20 = 3
k (-12) = -12 + 20 = 8
k(14) = 14 + 20 = 34
K (d+17) = (d+17) + 20 = d + 37


Geometry_proofs/257494: Given: Triangle ABC
Prove: m<4= m<1 + m<2
Picture: A triangle with line, CD, connected to it. A is m<1, B is m<2, C is m<3, and m<4 are vertical angles to m<3
1 solutions

Answer 189420 by drk(1908) About Me  on 2010-01-16 13:33:29 (Show Source):
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This is also called the exterior triangle theorem. With angle 4 vertical to angle 3, you cannot prove
angle 4 = angle 1 + angle 2. For this to work, angle 4 must be supplementary to angle 3. Here is the proof for that.
STATEMENT 1: triangle ABC
REASON 1: given
STATEMENT 2: angle 1 + angle 2 + angle 3 = 180 degrees
REASON 2: definition of sum of angles of triangle
STATEMENT 3: angle 3 + angle 4 = 180
REASON 3: definition of supplementary angles
STATEMENT 4: angle 1 + angle 2 + angle 3 = angle 3 + angle 4
REASON 4: substitution [2,3]
STATEMENT 5: angle 1 + angle 2 = angle 4
REASON 5: subtraction property of equality


real-numbers/257495: Which set of numbers is not closed under multiplication? odd integers, even integers, prime numbers, or rational numbers.
1 solutions

Answer 189417 by drk(1908) About Me  on 2010-01-16 13:21:29 (Show Source):
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Primes are not closed under multiplication.
--
Look at each separately:
odd integers: odd x odd = odd [closed]
even integers: even x even = even [closed]
prime numbers: prime x prime = composite [NOT closed]
rational numbers: fraction x fraction = fraction [closed]


Geometry_proofs/257490: Given: AB and CD bisects each other at M
Prove: AD is parallel to BC
Picture: Two triangles connecting to get, kind of like a bow tie.
1 solutions

Answer 189415 by drk(1908) About Me  on 2010-01-16 13:14:27 (Show Source):
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STATEMENT 1: AB bisects CD at M
REASON 1:given
STATEMENT 2: AM congruent BM
REASON 2: definition of bisector
STATEMENT 3: CM congruent DM
REASON 3: definition of bisector
STATEMENT 4: angle CMB congruent angle AMD
REASON 4: definition of vertical angles
STATEMENT 5:triangle CMB congruent triangle AMD
REASON 5: SAS
STATEMENT 6: CB congruent AD
REASON 6: CPCTC
STATEMENT 7: angle CBM congruent angle DAM
REASON 7: CPCTC
STATEMENT 8: CB is parallel to AD
REASON 8: definition of parallel lines.


Rectangles/257489: you have 80 feet of fencing to enclose a rectangular region. what is the maximum area?
1 solutions

Answer 189413 by drk(1908) About Me  on 2010-01-16 13:09:36 (Show Source):
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The perimeter is
P = 2L + 2W or
80 = 2L + 2W
dividing by 2 we get
(i) 40 = L + W
THe area is
(ii) A = LW
solving (i) for L, we get
(iii) L = 40-W
substituting that in (ii), we get
(iv) A = (40-W)(W)
using completing the square, we get
A = -(W-20)^2 + 400
So, when W = 20, the max area is 400.


Equations/257488: 3/7x+5/9y=27 and 1/9x+2/7y=7
1 solutions

Answer 189411 by drk(1908) About Me  on 2010-01-16 13:04:48 (Show Source):
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The two equations are:
(i) %283%2F7%29x%2B%285%2F9%29y=27
(ii) %281%2F9%29x%2B%282%2F7%29y=7
multiply both equations by 63 to get
(iii) %2827%29x%2B%2835%29y=1701
(iv) %287%29x%2B%2818%29y=441
multiply (iii) by 7 and (iv) by -27 to get
(v) %28189%29x%2B%28245%29y=11907
(vi) %28-189%29x%2B%28-486%29y=-11907
adding down, we get
-241y+=+0
y = 0.
x = 63
{63,0)


Linear-systems/257487: 12a^2 + 36b^2 -43ab=0 factorize it
1 solutions

Answer 189409 by drk(1908) About Me  on 2010-01-16 12:59:14 (Show Source):
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Our equation was
12a%5E2+%2B+36b%5E2+-43ab=0
step 1 - rewrite in descending order to get
12a%5E2+-+43ab+%2B+36b%5E2+=+0
step 2 - factor to get
%283a-4b%29%284a-9b%29+=+0
step 3 - set each part = 0 and solve to get
a+=+%284%2F3%29b
a+=+%289%2F4%29b


Percentage-and-ratio-word-problems/257474: Amy paid $57.16 for a pair of shoes during a 35% off sale. What was the regular price? I am thinking that the original price was $163.14 but not sure if I am right.
1 solutions

Answer 189408 by drk(1908) About Me  on 2010-01-16 12:55:16 (Show Source):
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If reduce a price by 35%, you still have 65% left.
So,
.65P = 57.16
dividing we get
p ~ $87.94.
--
checking,
87.94*.35 ~ 30.78
87.94 - 30.78 ~ 57.16.


Proportions/257482: the antecedent and consequent of a ratio differ by 40 and is equal to 2/7. find the ratio.
1 solutions

Answer 189407 by drk(1908) About Me  on 2010-01-16 12:52:07 (Show Source):
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We have a fraction of the following type
N/D, where D NOT = 0.
Based on the given information,
D - N = 40
and
N/D = 2/7.
This is a reduced number.
D = 40 + N
by substitution, we get
N / (40+N) = 2/7
cross multiply to get
7N = 80 + 2N
solve for N to get
5N = 80
N = 16
Since N = 16, D = 56
Our fraction is 16/56.


Proportions/257485: if a number of two digits is divided by th number obtained after reversing the digits, we get 2.08 , if the sum of the digit is 7, find the number.
1 solutions

Answer 189406 by drk(1908) About Me  on 2010-01-16 12:47:38 (Show Source):
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Let the original number be expressed as
10t+%2B+u
When you reverse the digits, you get
10u+%2B+t
Now the quotient = 2.08 as
%2810t%2Bu%29%2F%2810u%2Bt%29+=+2.08
We also know that t + u = 7, so t = 7-u. We get
%2810%2A%287-u%2Bu%29%29%2F%2810u%2B7-u%29+=+2.08
This gives us
%2870-9u%29%2F%289u%2B7%29+=+2.08
cross multiplying, we get
70-9u+=+18.72u+%2B+14.56
solving for u, we get
55.44+=+27.72u
u+=+2
t+=+5
original number is 52
reversed number is 25.
quotient is 2.08


Graphs/257483: I did this linear equation problem, but I want to make sure it is right.
Graph a line using the "friendly numbers" -2, -1, 0, 1, 2
1. y = 2x + 3 This is the answer I put down:
x / 2x+3 / y / (x,y)
-2 / 2(-2)+3 / -1 / (-2,-1)
-1 / 2(-1)+3 / 1 / (-1,1)
0 / 2(0)+3 / 3 / (0,3)
1 / 2(1)+3 / 5 / (1,5)
2 / 2(2)+3 / 7 / (2,7)
I didn't know how to make columns on the computer for my answers. The
above should be in columns, but I put slashes to indicate the columns. Now I am thinking about the answer because it states to a graph a line using the friendly numbers. Are my columns enough or do I have to graph a line?
1 solutions

Answer 189405 by drk(1908) About Me  on 2010-01-16 12:40:23 (Show Source):
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Everything you have is correct. You have created the x,y coordinates. You still have to graph these.
+graph%28+300%2C+200%2C+-2%2C+2%2C+-10%2C+10%2C+2x+%2B+3%29+


Proportions/257478: if y/x-z = y+x/z =x/y then find x:y:z
1 solutions

Answer 189404 by drk(1908) About Me  on 2010-01-16 12:37:27 (Show Source):
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A solution occurs when x = 4k, y = 2k, and z = 3k where K >=1. So,
x:y:z = 4:2:3


Equations/257415: a motorist drove a for 2 hours at one speed & then for 3 hours at another speed & one hour at the second speed, he would have covered 2444km. find the two speeds.
1 solutions

Answer 189403 by drk(1908) About Me  on 2010-01-16 12:28:03 (Show Source):
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This is an RTD problem. Here is a table base on given information:
motorist . . . . . . . . .rate . . . . . . . . . .time . . . . . . . . . .distance
. . . . . . . . . . . . . . .. R1 . . . . . . . . . . . .2 . . . . . . . . . .. . 2R1
. . . . . . . . . . . . . . . .R2 . . . . . . . . . . . .3 . . . . . . . . .. . .3R2
. . . . . . . . . . . . . . . R2 . . . . . . . . .. . . . 1 . . . . . . . . .. . .1R2
. . . . . .. . . . . . . . . . .. .. . . . . . . . . . .6 . . . . . .. . . . . . .2444
We see that
(i) 2R1+%2B+4R2++=+2444
or dividing by 2, we get
(ii) R1+%2B+2R2+=+1222
and that the average rate is
avgR = 2444/6 = 407.33
This means that
(iii) %28R1%2BR2%29%2F2+=+407.33
or
(iv) R1+%2B+R2+=+814.66
substituting (iv) into (ii) we get
(v) R1+%2B+R2+%2B+R2+=+1222
(vii) 814.66+%2B+R2+=+1222
solving for R2, we get
R2+=+407.33
This makes R1
R1+=+407.33
--
The rates appear to be the same.


Triangles/257424: The equal sides of an isosceles triangle have lengths of (5x – 30) and (3x + 10).
What is the greatest possible integer value of the third side?
1 solutions

Answer 189398 by drk(1908) About Me  on 2010-01-16 12:10:22 (Show Source):
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We set the two sides equal to each other as
5x – 30 = 3x + 10
Solving for x, we get
2x+=+40
x+=+20
Now, each side is worth 70.
We have a 70, 70, and x sided triangle.
Using the triangle inequality theorem, we get
70-70 < x < 70+70
or
0 < x < 140.
The greatest integer < 140 is 139.


Quadratic_Equations/257472: what is the axis of symmetry of this equation
y=2x2+8x-2

1 solutions

Answer 189396 by drk(1908) About Me  on 2010-01-16 12:06:43 (Show Source):
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To find axis of symmetry, we use -b/2a. So,
-b/2a = -8/2(2) = -8/4 = -2
The axis of symmetry is
X = -2.


Problems-with-consecutive-odd-even-integers/257473: find three cosecutive odd integers such that the sum of the least and greatest is 78
1 solutions

Answer 189395 by drk(1908) About Me  on 2010-01-16 12:05:21 (Show Source):
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Let x, x+2, x+4 b the 3 consecutive odd integers.
From the given, we get
x+ (x+4) = 78
2x + 4 = 78
2x = 74
x = 37
So, we get
37, 39, 41.


Human-and-algebraic-language/257470: A math test has a bonus question. The directions simply state that if you answer the question correctly you will recieve 5 bonus points and your test grade will be increased by 7% of your score. Let x = test score before answering the bonus question.
a) write a function, f(x) to represent just the 5 bonus points
b) Write a function, g(X) to represent just the precent of increase.
c) Explain the meaning of f(g(x))
d) Explain the meaning of g(f(x))
e) Does f(g(x)) = g(f(x)) in the problem? Explain
**** Please help me answer all these questions, i really dont understand. Please and thank you!
1 solutions

Answer 189393 by drk(1908) About Me  on 2010-01-16 12:03:55 (Show Source):
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X is the number of points.
First we have a proportion
5/N = 7/100
Solving, we get n ~ 71.42 or ~ 71.
There are 71 points on this test.
a) write a function, f(x) to represent just the 5 bonus points
ANSWER:
f%28x%29+=+x+%2B+5
b) Write a function, g(x) to represent just the precent of increase.
ANSWER:
g%28x%29+=+100%2A%28x%2B5%29%2F71
c) Explain the meaning of f(g(x))
ANSWER: The g(x) is a percentage which you then add to a number of points.
d) Explain the meaning of g(f(x))
ANSWER: f(x) is a raw score that you are converting into percentage
e) Does f(g(x)) = g(f(x)) in the problem? Explain
They are not the same.
f(g(x)) = (100x+855)/71
g(f(x)) = (100x + 1000)/71


Permutations/257467: Find the probability that the sum of the values of two dice in a throw of two fair dice is 8, given that the one die is 5.
1 solutions

Answer 189388 by drk(1908) About Me  on 2010-01-16 11:28:34 (Show Source):
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Given one die is 5 we could have (5,3) or (3,5). So,
P (sum = 8, given one is 5) = 2/36 = 1/18.


Permutations/257468: An urn contains 3 white balls and 5 red balls. Two balls are drawn at random. If the first is replaced before the second is drawn, what is the probability that the first ball is white and the second is red?
1 solutions

Answer 189387 by drk(1908) About Me  on 2010-01-16 11:27:04 (Show Source):
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P(white then red) = 3/8*5/8 = 15/64.
Since we are replacing, the denominator stays the same.


Permutations/257469: Five cards are dealt at random from a regular deck of 52 playing cards. Find the probability that three are sevens.
1 solutions

Answer 189386 by drk(1908) About Me  on 2010-01-16 11:25:39 (Show Source):
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This is a combination problem. We want 3 of the 4 sevens and don't care about the other cards. SO, we have
p(3 sevens) = (4c3)*(48c2) / (52c5) ~ 0.001736


Average/257427: After ten tests, Bryan’s average test grade was 84. His teacher decided to drop each student’s lowest and highest test grade. This brought Bryan’s average up to 85. If his lowest test score (of the original 10 tests) was 24 points lower than his highest test, what was his highest test grade?
1 solutions

Answer 189385 by drk(1908) About Me  on 2010-01-16 11:23:04 (Show Source):
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So, we know that the average of 10 tests is 84. This is a total of 840 points.
We know the average of 8 tests is 85. his is a total of 680 points.
Let the highest score = H and the lowest score = H - 24.
--
8 tests + 2 dropped tests = 10 tests. SO, we get
680 + 2H - 24 = 840.
solving for H, we get
2H = 840 - 680 +24
2H = 184
H = 92
H-24 = 68
HIs highest grade was 92.


Angles/257432: if a and b are complementary angles and a is 10 degrees greater than b, what size is angle b?
1 solutions

Answer 189383 by drk(1908) About Me  on 2010-01-16 11:17:54 (Show Source):
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We know that
a + b = 90
a = b + 10
By substitution we get
b+ 10 + b = 90
2b + 10 = 90
2b = 80
b = 40.


Geometry_Word_Problems/257435: A cone sits on top of a cylinder. Both have a radius of 3. The heights of the
cylinder and cone are 8 and 4 respectively. Determine the exact volume of the
combined solid.
1 solutions

Answer 189382 by drk(1908) About Me  on 2010-01-16 11:16:17 (Show Source):
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Lets first find the volume of the cylinder.
We have
V+=+pi%2Ar%5E2h
V+=+pi%2A3%5E2%2A8
V+=+72pi
--
Now the volume of the cone
We have
V+=+%281%2F3%29Bh
V+=+%281%2F3%29pi%2Ar%5E2%2Ah
V+=+%281%2F3%29%2Api%2A3%5E2%2A4
V+=+12pi
--
adding these we get
V+=+84pi


Proportions/257438: Determine the value of n so that the roots of nx^2 – 8x + 10 = 0 are equal.
1 solutions

Answer 189381 by drk(1908) About Me  on 2010-01-16 11:13:08 (Show Source):
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Here is our equation
(i) nx^2 – 8x + 10 = 0
We need the discriminant part of the quadratic which is
(ii) D+=+b%5E2-4ac
From (i), the D is
(iii) D+=+64+-+4%2An%2A10
We want The roots to be equal, so D = 0.
From (iii) we get
(iv) 64+-+4%2An%2A10+=+0
Solving for n, we get
64+-+40n+=+0
40n+=+64
n+=+8%2F5


Miscellaneous_Word_Problems/257445: Snow White and the Seven Dwarfs went to work as carpenters. Each dwarf earned $20.
Snow White earned $3.50 more than the average of the eight. How much did Snow White earn?
1 solutions

Answer 189378 by drk(1908) About Me  on 2010-01-16 10:59:55 (Show Source):
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We can write an equation based on the given information. Let S = snow white. The 7 dwarfs + snow white = 8 people.
%28%287%2A20%29+%2B+S%29%2F8+%2B+3.50+=+S
multiply all by 8 to get
140+%2B+S+%2B+28+=+8S
subtract S and combine like terms to get
168+=+7S
diving, we get
S = $24


Miscellaneous_Word_Problems/257446: If one skip equals four hops and if one jump equals three skips, what is the total number of hops in a hop, a skip, and a jump?
1 solutions

Answer 189376 by drk(1908) About Me  on 2010-01-16 10:55:52 (Show Source):
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We have the following:
(i) 1S+=+4H
(ii) 1J+=+3S
rewrite (i) as
(iii) 3S+=+12H
this will help with the conversion of J.
--
1H = 1H
1S = 4H
1J = 3S = 12H


Proportions/257461: if 6a^2-ab:2ab-b^2=6:1 find the a:b
1 solutions

Answer 189374 by drk(1908) About Me  on 2010-01-16 10:52:03 (Show Source):
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We have the following:
%286a%5E2-ab%29%2F%282ab-b%5E2%29=6
cross multiplying, we get
6a%5E2+-+ab+=+12ab+-6b%5E2
setting the equation = 0, we get
6a%5E2+-+13ab+%2B+6b%5E2+=+0
factoring, we get
%282a-3b%29%283a-2b%29=0
solving each we get
a/b = 3/2
a/b = 2/3
So, we have two answers:
a:b = 3:2
a:b = 2:3


Permutations/257465: . A single card is drawn at random from a deck of 52 cards. Jack, Queen, and King are considered the only picture cards. Find the probability that the card will be a picture card.
1 solutions

Answer 189373 by drk(1908) About Me  on 2010-01-16 10:45:55 (Show Source):
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There are 4 jacks, 4 queens, and 4 kings for a total of 12.
P(face card) = 12/52 = 3/13


Linear_Equations_And_Systems_Word_Problems/257464: a shipper box is 14 1/2 in lenght by 9 1/8 wide by 8 11/16 high whats the volume in cubic ft rounded to the nearest 100th of a cubic ft.
1 solutions

Answer 189372 by drk(1908) About Me  on 2010-01-16 10:45:01 (Show Source):
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I would suggest writing all of these as improper fractions and then multiplying like this:
%2829%2F2%29%2A%2873%2F8%29%2A%28139%2F16%29
unfortunately, nothing cancels, so we get
294263%2F256
Here it is a matter of division to get
1149.46484
rounded, we get
1149.465 cu. ft.