What is the lowest grade for the 5th exam that he can get to earn a 90%?

Question

Jay scored a 92, 87, 89, and 94 on the past 4 assessments. What is the lowest grade for the 5th exam that he can get to earn a 90%?

Answer 1

the underlying formula that you want to use to solve here is

(92 + 87 + 89 + 94 + x) / 5 = 90(5)

solving that algebraically for the value of "x" yields

362 + x = 450

x = 88

meaning that to maintain his 90% average he needs to score an 88 on the 5th exam

Answer 2

Okay, we can do this! First, we need to add up all of the scores, even the ones we don't know yet:

92 + 87 + 89 + 94 + X

362 + X

Now then: we need to find the average grade, and that means totaling them up (we did that already!) and dividing by the number of terms (5). Like this:

(362 + x) / 5 ≥ 90

Multiply both sides by 5 and we get:

362 + X ≥ 450

-362        -362

          X ≥  88See? We're done already!