Time taken to produce widgets

[gmattesttaker2]

Hello,

For the following:

If Machine X can produce 80 widgets in 4 hours, how long would it take machine X and Y working together, to produce 500 widgets?

1.Machine Y works at 3/4 the speed of machine X
2.If Machine Y's speed doubled, it would produce 120 widgets in 4 hours

OA: D

Machine X produces 20 widgets per hour. Does Statement 1 mean that Machine Y's speed is 3/4(20) = 15 widgets per hour?

Thanks a lot,
Sri

[theCodeToGMAT]

X = 80 widgets = 4 hr ==> 1hr = 20 W

X & y together =500

We need to find Y's speed

Statement 1:
Y = 3/4 * X
We can get Y's speed
SUFFICIENT


Statement 2:
2 * y = 120 W in 4 Hr
SUFFICIENT

[spoiler]{D}[/spoiler]

[theCodeToGMAT]

Hello,

Machine X produces 20 widgets per hour. Does Statement 1 mean that Machine Y's speed is 3/4(20) = 15 widgets per hour?

Yes!

[ceilidh.erickson]

Does Statement 1 mean that Machine Y's speed is 3/4(20) = 15 widgets per hour?

The answer is... it doesn't matter! Because this is a DS question, you don't actually have to do the math here.

First, figure out what your target question really is:

Given: If Machine X can produce 80 widgets in 4 hours, how long would it take machine X and Y working together, to produce 500 widgets?

Infer: If we know X's time and output, then we know X's rate: 80/4. If we want to know the time it would take X and Y working together, then we need Y's rate.

1.Machine Y works at 3/4 the speed of machine X
Don't waste time doing the math here! We know X's rate, so we can use this to get a value for Y's rate. Then we would be able to add X's and Y's together and solve for the time - but we don't need to actually do that!

2.If Machine Y's speed doubled, it would produce 120 widgets in 4 hours
If we are given information about twice Y's rate, then we can solve for Y's rate. Once again, don't actually do that math!

The answer is D.