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Working at their respective constant rates, machine A makes [#permalink]

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09 Mar 2011, 15:03

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41% (02:21) correct
59% (01:35) wrong based on 237 sessions

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Working at their respective constant rates, machine A makes 100 copies in 12 minutes and machine B makes 100 copies in 15 minutes. If a number of x machine A and a number of y machine B work simultaneously at their respective rates for 2 hours, what is the total number of copies that they will produce?

Re: Working at their respective constant rates, machine A makes [#permalink]

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09 Mar 2011, 17:00

banksy wrote:

268. Working at their respective constant rates, machine A makes 100 copies in 12 minutes and machine B makes 100 copies in 15 minutes. If a number of x machine A and a number of y machine B work simultaneously at their respective rates for 2 hours, what is the total number of copies that they will produce? (1) x = y. (2) 5x + 4y = 90.

can't find the the total copies that they will produce without knowing the value of x and y. So with (1) and (2), it is sufficient to find values. Answer C.

Re: Working at their respective constant rates, machine A makes [#permalink]

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09 Mar 2011, 23:56

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banksy wrote:

268. Working at their respective constant rates, machine A makes 100 copies in 12 minutes and machine B makes 100 copies in 15 minutes. If a number of x machine A and a number of y machine B work simultaneously at their respective rates for 2 hours, what is the total number of copies that they will produce? (1) x = y. (2) 5x + 4y = 90.

Rate of Machine A is 100/12 copies per minute and that of Machine Y is 100/15 copies per minute.

When x number of A machines and y number of B machines work simultaneously at their respective rates for 2 hours (120 minutes), they will produce \(120*((100/12)*x+(100/15)*y)\)copies

\(120*((100/12)*x+(100/15)*y)\) on simplification becomes \(200*(5x+4y)\)

Statement 1 says \(x=y\), which doesn't help us get the exact numbers, so insufficient

Statement 2 says \(5x+4y = 90\), we cant solve for x and y from this, but all we need to answer the question is value of 5x+4y which we get from this statement, so sufficient.

Re: Working at their respective constant rates, machine A makes [#permalink]

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10 Mar 2011, 00:11

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Mongolia2HBS wrote:

banksy wrote:

268. Working at their respective constant rates, machine A makes 100 copies in 12 minutes and machine B makes 100 copies in 15 minutes. If a number of x machine A and a number of y machine B work simultaneously at their respective rates for 2 hours, what is the total number of copies that they will produce? (1) x = y. (2) 5x + 4y = 90.

can't find the the total copies that they will produce without knowing the value of x and y. So with (1) and (2), it is sufficient to find values. Answer C.

subhashghosh wrote:

(1) is clearly insufficient.

For (2), several answers are possible:

5 * 14 + 4 * 5 = 90

5 * 10 + 4 * 8 = 90

But (1) and (2) together give x = y = 10, so answer is C

Guys, we are not concerned here with exact values of x and y. All we need to find is the total number of copies the machines working together would produce. So, anything that gives us their combined relationship is sufficient. Statement 2 effectively is telling us about that relationship.

So, statement B is sufficient to answer the given question.

Irrespective of whatever value x and y individually may have, as long as 5x+4y is 90, the number of pages they will produce would remain 200*90

We can easily check the same by putting different values for x and y.

Re: Working at their respective constant rates, machine A makes [#permalink]

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15 Dec 2014, 10:50

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Re: Working at their respective constant rates, machine A makes [#permalink]

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29 Dec 2015, 10:50

Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

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Re: Working at their respective constant rates, machine A makes [#permalink]

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13 Feb 2016, 22:05

banksy wrote:

Working at their respective constant rates, machine A makes 100 copies in 12 minutes and machine B makes 100 copies in 15 minutes. If a number of x machine A and a number of y machine B work simultaneously at their respective rates for 2 hours, what is the total number of copies that they will produce?

(1) x = y. (2) 5x + 4y = 90.

One big trap .A great leveller of sort.
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Re: Working at their respective constant rates, machine A makes [#permalink]

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29 Feb 2016, 20:17

banksy wrote:

Working at their respective constant rates, machine A makes 100 copies in 12 minutes and machine B makes 100 copies in 15 minutes. If a number of x machine A and a number of y machine B work simultaneously at their respective rates for 2 hours, what is the total number of copies that they will produce?

(1) x = y. (2) 5x + 4y = 90.

X*2*(100/12) + Y*2*(100/15) - No.of copies.

Multiply by 60.

200*(5X+4Y)=No. of copies. B Sufficient.

gmatclubot

Re: Working at their respective constant rates, machine A makes
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29 Feb 2016, 20:17

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