Chapter 4.6, Problem 40E

To determine

To find: The number of answers to bring his average up to $70\%$ .

Answer to Problem 40E

TheTodd have to solve the 10 questions more to bring his average up to $70\%$ .

Explanation of Solution

Given:

Todd has answered 11 of his last 20 daily quiz questions correctly and his baseball coach told him that he must bring his average up to at least $70\%$ .

Calculation:

As Todd has answered 11 of his last 20 daily quiz questions correctly and his baseball coach told him that he must bring his average up to at least $70\%$ .

The function become,

  $\frac{11+x}{20+x}=\frac{70}{100}$

Solve the given inequality.

  $\begin{array}{c}\frac{11+x}{20+x}=\frac{70}{100}\\ \left(11+x\right)100=70\left(20+x\right)\\ 110+10x=140+7x\\ x=10\end{array}$

Therefore, the Todd have to solve the 10 questions more to bring his average up to $70\%$ .