Question

Circle A has a radius of 9 centimeters and Circle B has a diameter of 19 centimeters. What is the relationship between the circumferences of Circle A and Circle B?

Answer 1

18:19

Explanation:

Given that,

The radius of circle A = 9 cm

The diameter of circle B = 19 cm

We know that,

Radius = diameter/2

The radius of circle B = 19/2 cm

The circumference of circle A is :

`C_A=2\pi r_A` ....(1)

And that of circle B is :

`C_B=2\pi r_B` ....(2)

Dividing equation (1) and (2) :

`(C_A)/(C_B)=(2\pi r_A)/(2\pi r_B)\\\\=(r_A)/(r_B)\\\\=(9)/((19)/(2))\\\\(C_A)/(C_B)=(18)/(19)`

Hence, the ratio of circumferences of Circle A and Circle B is 18:19.