GMAT Quantitative Practice, Problem Solving
If p Ο q = p(q – p), which of the following specific operations yields 2p – 4 ?
- 2p Ο 2
- p Ο 2
- 2p Ο p
- 2 Ο 2p
- 2 Ο p
This problem involves a defined operation and is essentially an exercise in algebraic substitution. For each answer choice, "plug" the given values into the expression p(q – p).
You can eliminate the first three listed operations because each one yields a quadratic expression containing a p2 term. The operation given in choice (E) is the one that yields 2p – 4:
p(q – p) = 2(p – 2) = 2p – 4
The correct answer is (E).