Math+in+everyday+life

What are some ways that math is used everyday? Talk to your relatives, neighbors, grocery store personnel, whomever and let's gather as many ways that math is used. If you already see the category on the list put a check next to it.

Have you ever come across an error in the newspaper, a magazine, heard one on TV especially in commercials, or, OMG, in a math book. Paste them here and let's discuss them.

Here's one that Mr. Wirtz pointed out. A particular fast food chain advertised 4 different meals under $4.00. If a family of four went and together ate four different meals should their bill be under four dollars? Why or Why not?