Chapter 13, Problem 1STP

To determine

Find the area of each washer to the nearest tenth.

Answer to Problem 1STP

B

Explanation of Solution

Given:

A machine is making steel washers by cutting out 10-millimeter circular disks from 34-millimeter circular disks .

  

Formula Used:

Area of a circle with radius r :

  $A=\pi r^2$

Calculation:

Let the large circle be $C_1$ with diameter 34 mm.

So,

radius , $r_1=\frac{34}{2}=17mm$

area , $A_1=\pi r_1{}^2=\pi {17}^2\approx 907.92m{m}^2$

Let the small circle be $C_2$ with diameter 10 mm.

So, radius , $r_2=\frac{10}{2}=5mm$

area, $A_2=\pi r_2{}^2=\pi 5^2\approx 78.54m{m}^2$

So, the area of washer is :

  $A_1-A_2\approx 907.92-78.54\approx 829.4m{m}^2$

So, the correct option is B.