OA from Princeton review
This is a Value Data Sufficiency question, so use the Pieces of the Puzzle approach to assess the question. Begin by determining “What is known” from the question stem and “What is needed” from the statements to answer the question. Determine “What is known.” The question asks for the area of triangle DGH. Draw and label parallelogram ABCD such that line segment AD represents the base of the parallelogram. Add points E, F, G, and H to the figure, so that line segment GD represents the base of triangle DGH, which occupies the parallelogram’s lower right corner. Whether or not the parallelogram is rectangular, the base of triangle DGH is one-fourth the base of parallelogram ABCD, and the height of triangle DGH is one-fourth the height of parallelogram ABCD. If bh represents the area of parallelogram ABCD, then the area of triangle DGH is 1/2(1/4b)(1/4h) , or 1/32bh. Now, determine “What is needed.” In order to answer the question, the statement(s) must provide information sufficient to determine either the area of parallelogram ABCD or the base and height of triangle DGH. Evaluate the statements one at a time.
Evaluate Statement (1). If the area of parallelogram ABCD is 96 square units, then the area of triangle DGH is 1/32 *96 = 3 square units. Statement (1) is sufficient to answer the question, so write down AD.
Now, evaluate Statement (2). If the parallelogram is a rectangle with dimensions 8 by 12, then the base and height of triangle DGH are 2 and 3, and the area of the triangle is square units. However, if parallelogram ABCD is not a rectangle, then its sides are not perpendicular. In this case, the measures of the parallelogram’s interior angles are unknown, so it is impossible to determine the parallelogram’s height, and impossible to determine the triangle’s height. Statement (2) is insufficient to answer the question, so eliminate choice D. The correct answer is choice A.