was 70 the average grade on a class test?
1. on the test,half of the class had grades below 70 and half of the class had grades above 70.
2. the lowest grade on the test was 45 and the highest grade on the test was 95.
You can find out pretty quickly that the answer to this question is E.
St. (1) Examples:
15, 15, 75, 75 ... These scores fit the conditions of (1), and the average is 45.
69, 69, 71, 71 ... These scores fit the conditions of (1), and the average is 70.
INSUFFICIENT
St. (2) Examples:
45, 95 ... These scores fit the conditions of (2), and the average is 70.
45, 45, 95 ... These scores fit the conditions of (2), and the average is less than 70.
INSUFFICIENT
St. (1) and (2) together:
45, 45, 95, 95 ... These scores fit the conditions of (1) and (2), and the average is 70.
45, 46, 95, 95 ... These scores fit the conditions of (1) and (2), and the average is greater than 70.
INSUFFICIENT
Rich Zwelling
GMAT Instructor, Veritas Prep
