GMAT PREP Problems

I'm very skeptical about the second question; it says xy = 1, and then asks what 2(x+y)^2/2(x-y)^2 is equal to. Take x = 4 and y = 1/4 for example' xy = 1. (4+1/4)^2 = 18.0625. (4-1/4)^2 = 14.0625. When you divide 18.0625 by 14.0625, you do not get 16. Flag that question for review

1)
For Class A:
Range = r
Greatest Height = g
Hence least height La = g - r ( range = greatest - least)

For Class B:
Range = s
Greatest Height = h
Hence least height Lb = h-s

The statements are:

(1) r<s
(2) g>h

(1) r<s
hence g-r > g-s
But this is not sufficient.

(2)g>h
hence g-r > h-r
But this is not sufficient.

Combining (1) and (2)
g>h
hence g-r > h-r

r<s
Substitute s instead of r on RHS
hence g-r > g-s
So least height of A La > least height of B Lb

So, both (1) and (2) together are sufficient
Answer is C
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3)
imagine the set as { V1, V2, ... V73)
V1 falls in 50-59 etc
Total No of scores = 73
Hence median is (73+1)/2 = 37th score

The 37th value is in 80-89 range.

Hence answer is C