My daughter is learning geometry....so why not make the rest learn a little too ;) Ya have to understand, we are "sorta unschoolers", so this kind of thing, while dorky, is commonplace for us.
First, you need to know the formula for the area of a circle.
Next, ask your kids what is cheaper per square inch: a small, medium, or large pizza. The answers will vary depending on the size of pizzas your fav pizza place serves. In general, the answer is large....
Then, we had a buy one get one pizza free deal....so I had them compute what would be cheapest per square inch and for the needs of our family....cuz I'm admittedly a cheap skate, and want the best deal.
Then, we had quite the discussion of how math really does apply to our every day lives.
I love it when food and school come together!