Suppose your average, after taking 4 quizzes, is 73 (out of 100). What must your average be on the next 5 quizzes to increase your average to 88 out of 100?

x = average of next 5 quizzes

4 * 73 = first 4 quizzes

There will be a total of 4 + 5 = 9 quizzes

Average of all quizzes = 88 = (4*73+5x) / 9

9*88 = 9 * (292 + 5x) / 9

792 = 292 + 5x

500 = 5x

X = 500/5 = 100

Next 5 quizzes need to average 100