Pizzas are sized by diameter. What percent increase in area results if Chantel's pizza increases from a 10-inch pizza to a 12-inch pizza?
The formula for the area of a circle is A = pi · r2
10-inch pizza: A = pi · 102 = 100pi = 314.159 (approximately)
12-inch pizza: A = pi · 122 = 144pi
Increase in size: 144pi - 100pi = 44pi = 138.230 (approximately)
Percent increase: amount of increase divided by original amount (the 10-inch pizza) times 100
= 138.230 / 314.159 x 100 = 44%