AAPL wrote:GMAT Paper Tests
List K consists of seven numbers. Is the average (arithmetic mean) of the seven numbers negative?
1) Four of the seven numbers in list K are negative.
2) The sum of the seven numbers in list K is negative.
Target question: Is the average (arithmetic mean) of the seven numbers negative?
Statement 1: Four of the seven numbers in list K are negative.
There are several scenarios that satisfy statement 1. Here are two:
Case a: List K = {-10, -10, -10, -10, 1, 1, 1}. Average = sum/7 = -37/7. The answer to the target question is
YES, the average IS negative
Case b: List K = {-1, -1, -1, -1, 10, 10, 10}. Average = sum/7 = 26/7. The answer to the target question is
NO, the average is NOT negative
Since we cannot answer the
target question with certainty, statement 1 is NOT SUFFICIENT
Statement 2: The sum of the seven numbers in list K is NEGATIVE.
Average = (sum of all 7 numbers)/7
So, we get: Average =
NEGATIVE/7 = some negative number
The answer to the target question is
YES, the average IS negative
Since we can answer the
target question with certainty, statement 2 is SUFFICIENT
Answer: B
Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
