Chapter 9.7, Problem 17OE

To determine

To express: the age in terms of b and c .

Answer to Problem 17OE

The age of Bob is $\frac{1}{3}(c-4)$ .

Explanation of Solution

Given information:

  $\begin{array}{l}b=\text{Bob's age}\\ c=\text{Claire's age}\end{array}$

Four years ago, Bob was one-third as old as Claire was.

Formula used:

Age problem.

Step1. The problem asks for the Bob’s age and Claire’s age now.

Step2. Let b = the Bob’s age now.

Let c = the Claire’s age now.

Step3. Use the facts of the problem to write two equations.

Step4. Solve the equations.

Calculation:

Consider ,

Let b = the Bob’s age now.

Let c = the Claire’s age now.

Age	Now	4years ago
Bob	$b$	$\frac{1}{3}(c-4)$
Claire	$c$	$c-4$

According to the question,

The age of Bob is

  $\begin{array}{l}=b=\frac{1}{3}(c-4)\\ =b=\frac{c}{3}-\frac{4}{3}\end{array}$

Hence, the age of Bob is $\frac{1}{3}(c-4)$ .