Using a stack of index cards, write a money amount on each card. Try to write several large amounts as well as a few smaller amounts to create a more challenging game. Show children how to move the decimal one place to the left in order to calculate 10 percent of a dollar amount. Allow children to flip through the index cards and tell you what 10 percent of each dollar amount is just by moving the decimal point.
Finding 10 percent of an amount can be quite easy, while finding five percent can be a little more challenging. Show children how to find 10 percent first, and then divide that amount in half to find five percent. Use the same index cards as in the previous activity, only now ask children to find five percent of the number. Provide another piece of paper for children who need to take notes or do a math calculation to figure it out.
Explain to children that it is customary to tip at least 15 percent for service at a restaurant. Tell them that since they already know how to calculate 10 percent and five percent, learning how to calculate a tip amount will be very easy. Use the same index cards and show children how to calculate 10 percent, divide that number in half and then add it to the original 10 percent in order to calculate a 15-percent tip.
Create a simple restaurant in your classroom. Have children make menus with prices and set tables like a real restaurant. Decide which students will be waiters and waitresses and which students will be restaurant patrons. The patrons will place an order with the wait staff, who will then add up the total amount of the bill. The patrons will be responsible for figuring out the appropriate 15-percent tip amount. Be sure all students have a chance to be the wait staff and the restaurant patrons.