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

Answer:

18:19

Step-by-step 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) :

$\dfrac{C_A}{C_B}=\dfrac{2\pi r_A}{2\pi r_B}\\\\=\dfrac{r_A}{r_B}\\\\=\dfrac{9}{\dfrac{19}{2}}\\\\\dfrac{C_A}{C_B}=\dfrac{18}{19}$

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