Kalino earned 85, 95, 93, and 80 points on the 4 tests, each worth 100 points

Kalino earned 85, 95, 93, and 80 points on the 4 tests, each worth 100 points, given so far this term. How many points must he earn on his fifth test, also worth 100 points, to average 90 points for the 5 tests given this term?

1. 87
2. 88
3. 90
4. 92
5. 97

Answer

The correct answer is E.

Let x be the unknown score. Then, the sum of all the scores is 85 + 95 + 93 + 80 + x, and the average is 90.

That means (85 + 95 + 93 + 80 + x)/5 = 90

To solve this equation, you can multiply both sides by 5 to get

85 + 95 + 93 + 80 + x = 450

x = 97