Gillian Mark's grades on the past five algebra quizzes are 77, 93, 86, 90, and 95. Find the least grade possible for her to make on the sixth quiz so that her average is 90.

Answer 1

(77 + 93 + 86 + 90 + 95 + x) / 6 = 90

Solve for x and finish from here.

Answer 2

Let x = the 6th quiz grade

(77+93+86+90+95+x)/6 ≥ 90

(441+x)/6 ≥ 90 Multiply both sides by 6 to get rid of the fraction

(441+x) ≥ 540 Subtract 441 from both sides of the equation

x ≥ 99 (Better study hard!)