Data Sufficiency

LUANDATO wrote:Working at their respective constant rates, machine A majes 100 copies in 12 minutes and machine B makes 100 copies in 15 minutes. If a number of x machine X 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.

The OA is B.

I'm really confused with this DS question. Please, can any expert assist me with it? Thanks in advanced.

The narration is not clear. I think this is what the question means.

LUANDATO 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 x numbers of machine A and y numbers of machine B work simultaneously at their respective rates for 2 hours, what is the total number of copies that they will produce?

Since in 12 minutes, one machine A makes 100 copies, thus in 2 hours (120 minutes), it will make (100/12)*120 = 1000 copies. This means that x numbers of machine A will make 1000x numbers of copies in 2 hours.

Similarly, since in 15 minutes, one machine A makes 100 copies, thus in 2 hours (120 minutes), it will make (100/15)*120 = 800 copies. This means that y numbers of machine A will make 800y numbers of copies in 2 hours.

Thus, they together will make 1000x + 800y copies in 2 hours.

1) x=y.

Cannot get the value of 1000x + 800y. Insufficient.

2) 5x+4y=90.

We want the value of 1000x + 800y, which can be manipulated as 200(5x + 4y). Thus, 200(5x + 4y) = 200*90 = 1800 copies. Sufficient.

The correct answer: B

Hope this helps!

-Jay
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