Every spring, our family goes to Maryland Day, the annual celebration on the campus of the University of Maryland. One one occasion a few years ago, I took my kids up to a pizza booth to get some lunch. Pepperoni slices were $4.50 and cheese slices were $4.00. I ordered 2 pepperoni slices and 1 cheese slice, which came to a total of:

$4.50 + $4.50 + $4.00 = $13.00

The woman in the booth, whom I estimated to be in her mid to late 20s, said, “$15, please.”

I asked, “How do you come up with $15?”

She replied, “2 times $4.50 is $9.00,” (correct so far), “plus $4 makes $15.”

I replied, “Sorry, but $9 + $4 = $13, not $15.”

She insisted that it was $15, and we went back and forth a few times on this.

Fortunately, I had exact change, and I handed her $13. I said, “Ma’am, it comes to $13, and here you are. Feel free to check with any of your colleagues. Have a nice day.”

Experiences like this are among the reasons that math is a subject that is near and dear to my heart.

I’m not asking for integral calculus or a proof of Fermat’s Last Theorem. But I don’t think it’s too much to ask somebody at a pizza booth to perform basic arithmetic, especially when the numbers have dollar signs in front of them and when my money is involved in the transaction.