The radius of a circle is tripled. what happens to the area of the circle?

a) area is multiplied by 3

b) area is multiplied by 9

c) area is multiplied by 6

d) area is multiplied by 1/3

Answer is b) area is multiplied by 9

b) area is multiplied by 9

Explanation:

The formula of the area of a circle is A = π*r^2. If the radius is tripled, this means that you'll multiply the radius by 3, so the new radius will be 3r. If you do the formula with this new value you will get:

A = π * (3r) ^2

A = π*9r^2

So the effect on the area is that it will increase nine times.