Help please! im really confused and stuck

To find the area of a circle, use the following formula; A = πr^2

The radius of a circle is half the diameter.

So;

4.) 18/2 = 9

Radius = 9

(3.14)9^2

9(9) = 81(3.14)

254.34 is the area of figure #4.

5.) 12/2 = 6

A = (3.14)(6)^2

A = (3.14)(36)

113.04(2) Because there are two pizzas.

226.08

Number 4 gives the most amount of pizza. So, one 18 in. pizza.