Gregory has scored 91, 76, and 84 on the first three exams in his math class. If the standard 70,80,90 scale is used for grades of C, B, and A, and the exams are equally weighted, what is the minimum he can score on the final exam in order to:a) get a C average on exams?b) get a B average on exams? c) get an A average on exams?

Question

Answer:

a) (91+76+84+x)\4=70
(251+x)\4=70
251+x=280
x=29

b)(91+76+84+x)\4=80
(251+x)\4=80
251+x=320
x=69

c)(91+76+84+x)\4=90
(251+x)\4=90
251+x=360
x=109