The GMAT would specify that x is positive:
amarzouk wrote:If x/y = – 10 and x>0, what percentage of x is x – 10y ?
(A) 10% (B) 200% (C) 50% (D) 100% (E) Cannot be determined
x = -10y.
An alternate approach is to plug in values.
Since one of the answer choices is
cannot be determined, test two cases to confirm that each case yields the same percentage.
Case 1: y=-1, x=10
Here, x - 10y = 10 - (10)(-1) = 20.
In this case, (x-10y)/x * 100 = 20/10 * 100 = 200%.
Case 2: y=-2, x=20
Here, x - 10y = 20 - (10)(-2) = 40.
In this case, (x-10y)/x * 100 = 40/20 * 100 = 200%.
In each case, the same percentage is yielded: 200%.
The correct answer is
B.
Last edited by GMATGuruNY on Mon Dec 02, 2013 5:18 am, edited 1 time in total.
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