GRE Sample Test 4 Quantitative Reasoning 2

Here you have triangle ABC—base BC has been extended on one side and there is an exterior angle drawn in and labeled 120°. You want to compare side lengths AB and BC. In any triangle, the largest side will be opposite the largest angle, so you want to see which of these sides is opposite a larger angle. Angle A is labeled 60°, but is angle C less than, equal to, or greater than 60? Notice that the adjacent angle is 120°—the two together form a straight line, so their sum is 180°. And 180 − 120 = 60, so angle C is a 60° angle. Since the angles are equal, the sides are equal, and the answeris (C).