Exercise 16 Page 493

Practice makes perfect

We want to find the circumference of a circle with radius of 3 inches. Let's represent this situation on the diagram!

Now, we can recall formula for the circumference C of a circle with radius r. C=2π r Let's substitute 3 for r in the formula and calculate C!

C=2π r

r= 3

C=2π( 3)

C=6π

π ≈ 3.14

C≈ 6( 3.14)

C≈ 18.84

The circumference of the circle is about 18.84 feet.

We want to find the circumference of the circle with a diameter of 27 centimeters. Let's represent this situation on the diagram!

Now, we can recall formula for the circumference C of a circle with diameter d. C=π(d) Let's substitute 27 for d in the formula and calculate C!

C=π(d)

r= 27

C=π( 27)

π ≈ 3.14

C≈ 3.14(27)

C≈ 84.78

The circumference of the circle is about 84.78 centimeters.

9.1.1 Circumference, Diameter, and Pi p.491-494

9.1.2 Area of Circles p.499-501

9.1.3 Area of Composite Shapes p.502-503

Hints