# Congruence and Similarity of Circles

## Interactive practice questions

We want to compare the circumference and area of two circles: circle A has radius $5$5 units and circle B has radius $40$40 units.

a

What is the circumference of circle A? Give your answer as an exact value.

b

What is the circumference of circle B? Give your answer as an exact value.

c

What is the area of circle A? Give your answer as an exact value.

d

What is the area of circle B? Give your answer as an exact value.

e

By what factor is the radius of circle A enlarged to give the radius of circle B?

f

By what factor is the circumference of circle A enlarged to give the circumference of circle B?

g

By what factor is the area of circle A enlarged to give the area of circle B?

Easy
Approx 5 minutes
A circle with a radius of $2$2 units is enlarged by a factor of $7$7.
Circle A has a perimeter measuring $10\pi$10π cm, while circle B has a radius measuring $10$10 cm.
The ratio of the circumference of circle A to the circumference of circle B is $\frac{4}{3}$43.