Bunuel wrote:

Sales associate Danielle has a weekly goal to average 75 phone calls per day. If her average for the first four days of a five-day workweek was 72 phone calls per day, how many phone calls does she need to make on the fifth day to reach her goal?

A. 75

B. 78

C. 81

D. 84

E. 87

I. Per day shortage4 days * 3 fewer calls/day than goal = 12 calls short

She must make up for the shortfall on Day 5

Day 5? 75 (reg) + 12 = 87 calls on Day 5

Answer E

II. \((A * n) = S\)Goal: average, A, of 75 calls/day for n=5 days

Goal total:

\((75 * 5) = 375 = Sum_1\)Average for Days 1-4 = 72 calls

Total?

\((72 * 4) = 288 = Sum_2\)The difference between sums equals the number of calls she must make on Day 5

\((375 - 288) = 87\) calls

Answer E

_________________

In the depths of winter, I finally learned

that within me there lay an invincible summer.

-- Albert Camus, "Return to Tipasa"