Exercise 59 Page 508

Use the formulas for finding the area and circumference of a circle.

Area: about 153.9 square centimeters
Circumference: about 44 centimeters

Practice makes perfect

We want to find the the circumference and the area of the circle. We can do each of these things one at a time.

Area

Let's consider the given diagram!

Notice that the circle has the radius of 7 centimeters. Now, we can recall formula for the area A of a circle with radius r. A=π r^2 Let's substitute 7 for r in the formula and calculate A!

A=π r^2

Substitute

r= 7

A=π( 7)^2

CalcPow

Calculate power

A=π(49)

UseCalc

Use a calculator

A=153.938040...

RoundDec

Round to 1 decimal place(s)

A≈ 153.9

The area of the circle is about 153.9 square centimeters.

Circumference

Now, we can calculate the circumference of the circle. Let's recall the formula for the circumference C of a circle with radius r. C=2π r Let's substitute 7 for r in the formula and calculate C!

C=2π r

Substitute

r= 7

C=2π( 7)

Multiply

C=14π

UseCalc

Use a calculator

C≈ 43.982297...

RoundDec

Round to 1 decimal place(s)

C≈ 44.50