diameter and area and money

Question

a pizza company charges $8.99 for its small pizza that has a diameter of 20 cm. the company charges $20.89 for its large pizza that has a diameter of 40 cm. which pizza is the better deal? explain your reasoning.

Answer 1

R = D/2 and area = pi * r^2

small pizza:

D = 20 ---> R=10 ---> Area = pi*10^2 = 314.16 square centimeters

$8.99 / 314.16 = 0.02861599185128596893302775655717 per square centimeter

large pizza

D=40 --> R=20 --> Area = pi*20^2 = 1256.637

20.89/1256.637 = 0.01662373461866871658243390891721‬ per square centimeter

small pizza is the better deal