A class comprises 40 students and is divided into two sections. In sec : Problem Solving (PS)

Given: A class comprises 40 students and is divided into two sections. In section A, the average score in a test was 85. In section B, the average score in the test was 80.
Asked: If the average score of the class in the test was 82, how many students are in section A?

Let the students in section A be x students.
Students in section B = 40 - x

Average score in the test = 82*40 = 3280 = 85x + 80(40-x) = 3200 + 5x
5x = 80
x = 16


IMO C

Bunuel wrote:A class comprises 40 students and is divided into two sections. In section A, the average score in a test was 85. In section B, the average score in the test was 80. If the average score of the class in the test was 82, how many students are in section A?

(A) 12
(B) 14
(C) 16
(D) 20
(E) 22

Solution:

We can create the equation where x is the number of students in section A:

[85x + 80(40 - x)] / 40 = 82

85x + 3200 - 80x = 3280

5x = 80

x = 16

Answer: C
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