If ABCD is a rectangle, what is the area of the shaded region?
A) 64
B) 82
C) 96
D) 120
E) 150

IMPORTANT: the diagrams in problem solving questions are DRAWN TO SCALE unless stated otherwise.

So, even though this is a tricky question, we can quickly eliminate 3 of the answer choices and have a 50-50 chance of guessing correctly. Here's how:

Rectangle ABCD has dimensions 15 x 20, so its area = 300.
So, the area of ∆BCD = 150 (half of 300)
So, the shaded area must have an area that's LESS THAN 150
So, we can eliminate E

Answer choices A and B are both APPROXIMATELY half of 150.
Does it look like half of ∆BCD is shaded?
NO.
So. we can eliminate A and B.

This leaves us with a guess between C and D

FINAL NOTE: The diagram provided here is obviously not drawn to scale, so unless there's some missing text (saying "not drawn to scale") that was supposed to accompany the diagram , this is not a GMAT-quality question.

Cheers,
Brent