$18

If you got this right you might have all the math you need for the course. You can check out a few astronomy problems to make sure, or you can go back to checking the latest on YouTube.

Explanation: The amount of pizza ingredients increase with the area of the pizza. However, the size of the pizza is the diameter. The pizza got 3 times larger (6 vs. 18).

A: You can reason that if you increase the diameter (or radius) of a circle then its area increases by the square of the increase. Three times the diameter results in 3²= 9 times the area so 9 x $2 = $18 for the cost

B: If you prefer a formula

The area of a circle = pi x radius²

area of the 6-inch pizza is pi x 6² = 113.1 square inches

area of the 18 inch pizza is pi x 18² = 1017.9 square inches which is 9 x larger than 113.1

Note two things: 1) pi is a constant and does not change so it does not affect any change in the area 2) you can do method A without a calculator Since you will not be allowed a calculator for the tests you might get used to method A.