Question

If the area of a circle is 81 pi square feet, find it's circumference

Answer 1

Step-by-step explanation:

since the area of a circle = π r², which is equal to 81 π feet²,

then we find the radius,

π r² = 81π feet²,

then r² = 81,

and lastly, r = 9 feet.

now the circumference of a circle = 2π r,

so, substituting the values,

$2 \times \pi \times r \\ = 2 \times \frac{22}{7} \times 9 \\ = \frac{44 \times 9}{7} \\ = \frac{396}{7} \\ = 56.5{approx.}$