Chapter 11, Problem 7SAP

To determine

To find: the correct option for the given condition.

Answer to Problem 7SAP

The option D is correct.

Explanation of Solution

Given information:

The condition is given as “if the average (arithmetic mean) of eight numbers is 20 and the average of five of these numbers is 14, what is the average of the other three numbers”.

Consider the condition.

if the average (arithmetic mean) of eight numbers is 20.

Then, the sum of eight numbers is,

  $\begin{array}{c}\frac{x_1}{8}=20\\ x_1=160\end{array}$

As the average of five of these numbers is 14.

Then, the sum of five numbers is,

  $\begin{array}{c}\frac{x_2}{5}=14\\ x_2=70\end{array}$

So, the sum of rest three number is,

  $\begin{array}{c}{x}_1-x_2=160-70\\ =90\end{array}$

The average of three numbers is,

  $\frac{90}{3}=30$

Therefore, the option D is correct.