Integrating math into other subject areas

Integrating math into other subject areas
I am looking for a few ways to integrate math concepts into various subject areas. I want to use Pi Day (March 14) specifically. Please help me come up with a list of 4-5 ideas for activities that could be done on this day in other classes, not just in math. I am really looking for œtried and true ideas that someone with teaching experience has successfully used.