Question

question 28, r3.6.39
part 1 of 2
the average, or mean, t, of three exam grades, z, w, and r, is given by the following formula. t = \frac{z + w + r}{3}
(a) solve the formula for r.
(b) use the formula in part (a) to solve this problem. on your first two exams, your grades are 84% and 88%; z = 84 and w = 88. what must you get on the third exam to have an average of 86%?
(a) the formula is r =

Explanation:

Step1: Multiply both sides by 3

$3T=z + w + r$

Step2: Isolate r

$r = 3T - z - w$

Step3: Substitute values for part (b)

Given $T = 86$, $z = 84$, $w = 88$. Then $r=3\times86 - 84 - 88$.

Step4: Calculate r

$r = 258-84 - 88=86$

Answer:

(a) $r = 3T - z - w$
(b) $86$