Chapter 4.5, Problem 13P

Write a function rule for the area of a rectangle whose length is 4 in. more than its width. What is the area of the rectangle when its width is 8 in.?

To determine

The function that describe the area of rectangle and area of rectangle for width 8 in.

Answer to Problem 13P

The function for area of rectangle is $A=b^2+4b$ .

The area of rectangle is $96\text{}{\text{in}}^{\text{2}}$ .

Explanation of Solution

Given:

Length is 4 in more than the width of rectangle.

Calculation:

Consider length and width of rectangle as l and b respectively.

The area of rectangle is expressed as follows:

  $\begin{array}{c}A=lb\\ =\left(b+4\right)b\left[l=b+4\right]\\ =b^2+4b\end{array}$

Thus, the function for area of rectangle is $A=b^2+4b$ .

Area of rectangle for width 8 in is calculated as follows:

  $\begin{array}{c}A=b^2+4b\\ =8^2+4\times 8\\ =96\text{}{\text{in}}^{\text{2}}\end{array}$

Thus, the area of rectangle is $96\text{}{\text{in}}^{\text{2}}$ .