Area: size of a pizza

As a math tutor, you notice these little surprises about everyday things.

We all know that, with a circle,

Area=Πr2.

Years ago, I worked in a pizza place. A small was 10″ (diameter), while a large was 14″. Let’s compare the sizes.

First, we’ll agree that from an eating point of view, the size of a pizza is really its area, rather than its diameter.

For the small, the diameter being 10″, its radius is of course 5″. Its area is

A=Πr2=Π(5)2=Π(25)≈78.5 square inches

For the large, the diameter being 14″, its radius is 7″, so its area is

A=Πr2=Π(49)≈154 square inches

The ratio of the areas:

large/small=154/78.5=1.96

I think we can agree that 1.96≈2.

Therefore, the 14 inch pizza is really twice the size of the 10 inch. You can check what kind of deal you’re getting on the large:)

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Leave a Reply