Question

The radius of a circle is 15. Using π, which equation expresses the ratio of the circumference to the diameter of a circle?

A: C=15πr

B: C15=π

C: C=r30π

D: C30=π

Answer 1

The equation which expresses the ratio of the circumference to the diameter of a circle is
`(C)/(30)=\pi` ⇒ D

Explanation:

π is the ratio between the circumference of the circle and the length of its diameter

`(C)/(d)=\pi` , where

• C is the circumference of the circle
• d is the diameter of the circle

∵ The circumference of the circle is C

∵ The radius of the circle is 15 units

∴ r = 15 units

- Find the diameter of the circle

∵ The diameter of the circle d = 2 r

∴ d = 2(15) = 30 units

∴ The diameter of the circle is 30 units

∵
`(C)/(d)=\pi`

∵ d = 30 units

∴
`(C)/(30)=\pi`

The equation which expresses the ratio of the circumference to the diameter of a circle is
`(C)/(30)=\pi`