thealchemist89 wrote:
Can anyone help me understand why my-setup is wrong?
Notice statement 1 and 2 are the same.
Correct answer is choice D. I chose answer choice E because my algebra came down to 3V2E. 3 variables but only 2 equations, therefor it is not sufficient, or I thought.
My setup was (#)(X) units = (250)(Y)? Trying to solve for #.
1.) 100X=625Y "100 units of currency X are equivalent to 625 unit of Y" (doesn't "of" mean multiply?)
2.) 2000X=12500Y
Hello theAlchemist89,
In trying to solve for #, you could have also taken the ratio approach. That would have helped you understand that this is just not another question on equations. Do not take the variable approach all the time, GMAT Math is about using smart numbers.
If you dig a little deeper, you will see that the individual statements are sufficient because they give us the ratio of X and Y. Let's see.
Statement I alone says that 100 basic units of X are equivalent to 625 basic units of Y. This means 100 * X = 625 * Y, which can be reorganised and written as X/Y = 4/25. This means that every 4 basic units of X is equivalent to 25 basic units of Y. This can help us find out the X equivalent of 250 units of Y.
Statement II alone says that 2000 basic units of X are equivalent to 12500 basic units of Y. This means 2000 * X = 12500 * Y, which can be reorganised and written as X/Y = 4/25. This again means that every 4 basic units of X is equivalent to 25 basic units of Y. This can help us find out the X equivalent of 250 units of Y.
That's how the individual statements are sufficient when taken alone. That's why the correct answer is D.
Also, 'Of' can mean multiplication but it's usually used with fractions, decimals, percentages etc., to signify 'so many times of'.
Hope that helps!
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95% (00:43) correct 
