Question

Christina's grade for her history class will be the average of

her midterm exam, final exam, and final paper. She received a
91 on her midterm and an 86 on her paper. What grade must
she get on her final exam to receive a grade of 90 for the
class? Explain using R.A.C.E.

Answer 1

The average is calculated by the sum of the total test scores divided by the total number of tests. This can represented in the equation:

91 + 86 + x /3 = 90

177 + x /3 = 90 ⇒ Multiply both sides by 3 to get rid of the /3

177 + x /3 x 3 = 90 (3)

177 + x =

177 - 177 + x = 270 - 177 ⇒ Subtract 177 from both sides to isolate x

x =93

Therefore, they must get 93% to end with a 90% final mark