Question

find the circumference and the area of a circle with radius 9 km. write your answers in terms of π, and be sure to include the correct units in your answers. (a) circumference: (b) area:

Explanation:

Step1: Recall circumference formula

The formula for the circumference of a circle is $C = 2\pi r$.

Step2: Substitute radius value

Given $r = 9$ km, so $C=2\pi\times9 = 18\pi$ km.

Step3: Recall area formula

The formula for the area of a circle is $A=\pi r^{2}$.

Step4: Substitute radius value

Given $r = 9$ km, so $A=\pi\times9^{2}=81\pi$ $km^{2}$.

Answer:

(a) Circumference: $18\pi$ km
(b) Area: $81\pi$ $km^{2}$