Question

1) Omar has scored 85, 71, and 77 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?

Answer 1

a. 47

b. 87

c. 127

Explanation:

Assume a total of 4 exams ( first 3 plus a final)

Let final score be X,

Hence, average score = (85 + 71 + 77 + x) / 4 = (233 + x) / 4

a) to get a C, the average score must be 70

70 = (233 + x) / 4

(233 + x) = 70 (4) = 280

x = 280 - 233 = 47 (Ans)

b) to get a B, the average score must be 80

80 = (233 + x) / 4

(233 + x) = 80 (4) = 320

x = 320 - 233 = 87 (Ans)

c) to get a A, the average score must be 90

90 = (233 + x) / 4

(233 + x) = 90 (4) = 360

x = 360 - 233 = 127 (Ans)