Hi LUANDATO,

We're told that John takes N tests, each containing 100 questions, and has an average score of 70%. We're asked for the number of correct answers John needs to score on the next test to raise his average to 72%. This question can be solved by TESTing VALUES.

IF... N=2
Then John took 2 tests and correctly answered (.7)(2)(100) = 140 questions of the 200 total questions.

With a 3rd test, John will then have answered 300 total questions. To get 72% of that overall total correct, he would need to answer (.72)(300) = 216 questions correct. He's already answered 140 questions correct, so he would need to answer 76 of the next 100 questions correctly to raise his overall average to 72%. Thus, we're looking for an answer that equals 76 when N=2. There's only one answer that matches.

Final Answer: D

GMAT assassins aren't born, they're made,
Rich