Question

A student has scores of 85,83,98 and 77 on four quizzes. What must she score on the fifth quiz to have an average of at least 84?

Answer 1

We need to find the solution to:
(85 + 83 + 98 + 77 + x) / 5 >= 84 where x is the score in the last test
This is the same as:
(343 + x) / 5 >= 84
Multiplying both sides by 5 we get
343 + x >= 420
Subtracting 343 from both sides we get
x >= 77

There for the student must get a score of at least 77 on the last tests.