Bunuel wrote:

On a given day, 50 people took a test that is designed to measure a candidate's aptitude. Some of the 50 people will take the test in the morning, and the remaining of the 50 people will take the test in the afternoon. What is the average (arithmetic mean) score on the test for the 50 examinees?

(1) The average score for the examinees who take the test in the morning was 68.2.

(2) The average score for the examinees who take the test in the afternoon was 74.3.

Combined..

We know the averages of each session BUT we require to know the ratio of students in each session.

Had it been half each, we could have got our Ans by taking average of the two averages .

E

_________________

1) Absolute modulus : http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372

2)Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html

3) effects of arithmetic operations : https://gmatclub.com/forum/effects-of-arithmetic-operations-on-fractions-269413.html

GMAT online Tutor