Hi swerve,

We're told that 60% of the people who responded to a company's advertisement for a job opening where interviewed over the phone and 20% of those interviewed over the phone (re: 3 people), were asked to come to the company for a personal interview. We're asked for the total number of people who responded to the advertisement. This question can be solved in a couple of different ways, including by TESTing THE ANSWERS.

Let's TEST Answer B first: 20 people
IF.... 20 people responded to the advertisement...
then (.6)(20) = 12 people were interviewed over the phone...
and (.2)(12) = 2.4 people had a personal interview.
This is NOT a match for what we were told (it's supposed to be 3 people, not "2.4 people"). This answer is too small, so we need MORE people to start with. Eliminate Answers A and B.

Under normal circumstances, we would TEST Answer D next.... but that Answer is DOUBLE Answer B (40 vs. 20) and that seems to be a big increase considering how closer 2.4 is to 3. So let's TEST Answer C next...

Answer C: 25 people
IF.... 25 people responded to the advertisement...
then (.6)(25) = 15 people were interviewed over the phone...
and (.2)(15) = 3 people had a personal interview.
This IS an exact match for what we were told, so this MUST be the answer!

Final Answer: C

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