statistics and percentages

Question

A student in a statistics class scored an 80%, 85%, and 90% on the first 3 tests. What must the student score on the last test to have at least a 87% in the class?

Answer 1

We require (0.8+0.85+0.9+x)/4≥0.87. Where x is the score needed on the 4th exam.

x = 0.87*4-0.8-0.85-0.9 = 0.99=3

So a score ≥93% is needed.