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Re: When the two painters work together and independently ? [#permalink]
yaser36 wrote:
When working alone, painter W can paint a room in 2 hours, and working alone, painter X can paint the same room in z hours. When the two painters work together and independently, they can paint the room in 3/4 of an hour. What is the value of z?
A) 3/4
B) 1[1/5]
C) 1[2/5]
D) 1[3/4]
E) 2


While I originally solved these types of problems by guessing and plugging in values and trying to set the fractions equal to each other, I have now learned a much more efficient way of solving these problems thanks to others on the board.

Painter W= 1 job/ 2 hours

Painter Z= 1 job/ x hours

Painter W and Z combined work rate= 1 job / 3/4 hour

1/2 + 1/x = 1/(3/4)
1/x= 1/(3/4)-1/2
1/x=4/3-1/2
1/x=8/6-1/2
1/x=8/6-3/6
1/x=5/6
x=6/5
x=1 1/5
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Re: When the two painters work together and independently ? [#permalink]
yaser36 wrote:
When working alone, painter W can paint a room in 2 hours, and working alone, painter X can paint the same room in z hours. When the two painters work together and independently, they can paint the room in 3/4 of an hour. What is the value of z?
A) 3/4
B) 1[1/5]
C) 1[2/5]
D) 1[3/4]
E) 2

let the total work be T, rate of worker W and X be w and x respectively

2w = T, w = T/2
xz = T, x = T/z

(w+x)*3/4 = T

Replacing w and x, we get

(T/2 + T/z)*3/4 = T

cancelling T and solving for z, we get
z = 6/5 or 1 1/5
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Re: When the two painters work together and independently ? [#permalink]
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yaser36 wrote:
When working alone, painter W can paint a room in 2 hours, and working alone, painter X can paint the same room in z hours. When the two painters work together and independently, they can paint the room in 3/4 of an hour. What is the value of z?
A) 3/4
B) 1[1/5]
C) 1[2/5]
D) 1[3/4]
E) 2


We are given that painter W can paint a room in 2 hours and that painter X can paint the same room in z hours. Thus, the rate of painter W is 1/2 and the rate of painter X is 1/z. We are also given that when they work together they can paint the room in 3/4 of an hour. Thus, their combined rate is 1/(3/4) = 4/3. We can create the following equation and determine z:

1/2 + 1/z = 4/3

Multiplying the equation by 6z, we have:

3z + 6 = 8z

6 = 5z

z = 6/5 = 1 1/5

Answer: B
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When the two painters work together and independently ? [#permalink]
yaser36 wrote:
When working alone, painter W can paint a room in 2 hours, and working alone, painter X can paint the same room in z hours. When the two painters work together and independently, they can paint the room in 3/4 of an hour. What is the value of z?
A) 3/4
B) 1[1/5]
C) 1[2/5]
D) 1[3/4]
E) 2


combined rate=1/2+1/z=4/3
1/z=4/3-1/2=5/6
inverting, z=6/5=1 1/5 hours
B
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Re: When the two painters work together and independently ? [#permalink]
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Re: When the two painters work together and independently ? [#permalink]
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