Chapter 12, Problem 12CR

a.

To determine

To calculate: The fourth proportion

Answer to Problem 12CR

The fourth proportion is $18$

Explanation of Solution

Given:

The measures of first three terms in a proportion are $5,3$ and $30$

Calculation:

Let the fourth proportion be x

  $\frac{5}{3}=\frac{30}{x}$

  $x=18$

Conclusion: Hence, the fourth proportion is $18$

b.

To determine

To calculate: The mean proportional between $8$ and $18$

Answer to Problem 12CR

The mean proportional between $8$ and $18$ is $12$

Explanation of Solution

Given:

First term = $8$

Last term = $18$

Concept used:

Here, we are using the formula:

  $b^2=$ first term $\times$ last term

(Where, “ b ” is middle term)

Calculation:

Here, $b^2=$ first term $\times$ last term

(Where, “ b ” is middle term)

  $b^2=8\times 18$

  $b=\sqrt{144}$

  $b=12$

Conclusion: Hence, the mean proportional between $8$ and $18$ is $12$