# Circle O has a circumference of 36π cm. Circle O with radius r is shown. What is the length of the radius r?

6cm, 18cm, 36cm, 72cm

**Solution:**

The circumference of the circle is the length around its circular region. The formula to find the circumference is c = 2πr.

where r is the radius of the circle.

Using the above formulae, 36π = 2πr

By dividing both the sides with 2π, we get

36π/2π = 2πr/2π

r = 18

Thus, the radius of the circle is 18cm.

## Circle O has a circumference of 36π cm. Circle O with radius r is shown. What is the length of the radius r?

**Summary:**

The length of the radius of the circle with center O has a circumference of 36π is 18cm.