Question

the area of a circle is 81pi? what is the diameter of the circle

Answer 1

What's the formula for the area of a circle?

Answer 2

Area = π × r2

Answer 3

Okay, now compare that with π × r2 = π × 81
it means r^2 must be 81, in that case, what's the radius?

Answer 4

it don't say

Answer 5

Of course it doesn't, you can find it... you know that r^2 = 81, so r must be equal to...?

Answer 6

is the answer 4.5?

Answer 7

the diameter is twice the radius

Answer 8

I got it now