Remind students of The Beat activity they previously completed. Ask for some examples of numbers we can reach in different ways (for instance, 8 is a number we say when counting by 2's, 4's, and 8's). Tell students you are thinking of a number. You say the number when counting by 3's and when counting by 5's. Can they guess the number?

You may allow students to work in small groups to strategize or individually. Students may practice skip counting by 3's and 5's and list the numbers they say in each. They may find multiple numbers (15, 30, 45, ...).

Next, ask them to narrow down their list by explaining your number can only be achieved by counting by 3's and 5's. That is, if any of their numbers can be achieved by counting by 10's or 9's, it isn't your number.

Students should determine your number must be 15. As 30 can be achieved by counting by 10's and 45 by counting by 9's, those should be eliminated. Some students may struggle with this warm up. Working in groups or asking students to make lists can help organize the information.

Extend the warm up by allowing students to create their own riddles and swap with a partner. This is a great pre-game activity for Hide and Seek.