Quote:
If x, y, and c are positive, is (x+c)/(y+c) > x/y?
1) y > x
2) c > y
Target question: Is (x+c)/(y+c) > x/y?This is a great candidate for
rephrasing the target question.
Aside: We have a free video with tips on rephrasing the target question: http://www.gmatprepnow.com/module/gmat-data-sufficiency?id=1100 Given: x, y, and c are positive This means that (y + c) is positive, which means we can take
(x+c)/(y+c) > x/y and safely multiply both sides by (y + c) to get:
(x+c) > (x/y)(y+c)Also, since y is positive, we can safely multiply both sides by y to get:
(y)(x+c) > (x)(y+c)Expand to get:
xy + yc > xy + xcSubtract xy from both sides to get:
yc > xcFinally, divide both sides by c to get:
y > xSo, we can REPHRASE the target question as.....
REPHRASED target question: Is y > x?At this point, it will take no time at all to analyze the two statements.
Statement 1: y > x PERFECT. This allows us to answer the
REPHRASED target question with certainty.
So, statement 1 is SUFFICIENT
Statement 2: c > y This does not help us answer the
REPHRASED target question with certainty.
So, statement 2 is NOT SUFFICIENT
Answer = A
Cheers,
Brent
_________________
Test confidently with gmatprepnow.com