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Working at their respective constant rates, machine A makes [#permalink]
09 Mar 2011, 14:03

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Difficulty:

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Question Stats:

36% (01:44) correct
64% (00:37) wrong based on 15 sessions

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.

Re: 268. Working at their respective constant rates, machine A m [#permalink]
09 Mar 2011, 16:00

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: 268. Working at their respective constant rates, machine A m [#permalink]
09 Mar 2011, 22:56

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: 268. Working at their respective constant rates, machine A m [#permalink]
09 Mar 2011, 23:11

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.

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