When ordering pizza – use fractions to discuss the slices and how many pieces everyone ate. I ate 1/2 while you ate 1/3. If I ate 1/2 of a small pizza and you ate 1/3 of an extra-large pizza, did I eat more? If I ate 1/2 of a pizza and you ate 4/8 of the same pizza, who ate more? Lots of authentic ways to teach fractions.
You can also teach the early vocabulary of fractions with young children. When discussing ordering a pizza you can use words like whole, half, and quarter. “Half” the pizza with cheese, and “Half” with pineapple and ham (my favorite). Hmmm…gotta go order pizza for lunch now!
Here is another math idea for children while eating at restaurants. My mom actually came up with this idea when I was a child and had discovered shrimp cocktails. To make us aware of how much we were spending at restaurants, she played a game called “Guess the Check.” After the first time, we would expect this, and my brothers and I would listen to everyone order, check the prices on the menu, and add up the cost in our heads. Not only was this a great way to develop authentic math skills, but it also made us aware of what we were ordering/spending at a restaurant. After a conversation about family budgets and eating out, my order of the expensive shrimp cocktail ceased (except when my grandparents came to town and were treating – that is what grandparents are for!)