Snack time is a great time to introduce your child to the concept of parts and wholes, especially if you use citrus fruit that can easily be divided into sections.
Peel an orange (or a grapefruit for a very sour snack) and divide it into halves. You both have the same amount of orange! Then invite your child to discover how many pieces she can make from her half. Wonder out loud if those pieces still make the same as your half. What if you divide your half now? Can you make the same number of pieces that she has?
For added fun, try sharing the sections you made with someone else. Can you make it so everyone gets the same?