Abby scored 58, 88, 102, 90 on her first four history quizzes. What scared does abby needs to get on her fifth quiz to have an average of exactly 85 on her history quizzes

Answer 1

87 is needed to boost the grade average to exactly 85

currently the average is (58+88+102+90)/4 = 338/4 = 84.5

to get 85, the next grade = x where (338+x)/5 = 85 or 5(85) = 338+x = 425, x = 425-338 = 87