Exercise 39 Page 720

What is the formula for finding the circumference of a circle?

Diameter: 0.25x
Circumference: 0.79x

Practice makes perfect

Let's find the length of the diameter and the circumference separately.

Diameter

To find the diameter, we can multiply the radius by 2. d = r * 2From the exercise, we know that the radius of the circle is x8. By substituting x8 for r in the formula, we can calculate d. d = x/8 * 2 → d = 0.25x The diameter of the circumference is 0.25x.

Circumference

The circumference C of a circle with radius r is calculated using the formula below. C=2π r From the exercise, we know that the radius of the circle is x8. By substituting x8 for r in the formula, we can calculate C.

C=2π r

Substitute

r= x/8

C=2π( x/8)

MoveLeftFacToNum

a*b/c= a* b/c

C=2π x/8

ReduceFrac

a/b=.a /2./.b /2.

C=π x/4

UseCalc

Use a calculator