Question

What is the radius of this circle if the circumference is 18 cm?

C=18 cm
3 cm
9 cm
18 cm
36 cm

Answer 1

Its B on ed. = 9 cm

Explanation:

Answer 2

r=2.86

Explanation:

The formula for the circumference of a circle is 2 times pi times the radius (2πr).

Set that equal to the number the problem gives you, and you see:

2πr=18 cm

Now solve for the radius by doing the opposite of what pi and 2 are doing mathematically with the r. (They are both multiplying by r, so we divide both sides of the equation by them to ‘move’ them off the left side of the equation.)

First divide each side by 2, and you get:

r=9 cm