Chapter 2.3, Problem 7ST

To determine

Bill’s score on his third test.

Answer to Problem 7ST

To attain the average of at least 80, Bill’s third test score must be greater than or equal to 83.

Explanation of Solution

Given:

Bill’s scores in first two tests were 75 and 82.

Average of his three tests should be at least 80.

Calculation:

Let Bill’s score on his third test be x.

Then, the given problem can be written as:

  $\begin{array}{l}\frac{75+82+x}{3}\ge 80\\ \frac{157+x}{3}\ge 80\\ 157+x\ge 240\\ x\ge 240-157\\ x\ge 83\end{array}$

Therefore, to attain the average of at least 80, Bill’s third test score must be greater than or equal to 83.