## Lesson: Adding and Subtracting Two-Digit Numbers and Money Amounts

Introducing the Concept

Begin by reviewing basic addition facts. When children demonstrate proficiency with these, explain that they will learn next how to add two-digit numbers. Ask them for examples of things in the classroom that would be represented by two-digit numbers, such as the number of books, desks, and coat hooks. Then ask them to suggest several examples of two-digit numbers and write them on the board.

**Materials:** blank transparency, overhead base-ten blocks, coins

**Preparation:** Draw a tens-and-ones frame on the transparency. Have children practice using a tens-and-ones frame and base-ten blocks to represent two-digit numbers.

**Prerequisite Skills and Concepts:** Children should have a solid grasp of the basic addition facts.

Write 34¢ and 52¢ in the tens-and-ones frame. Relate the dimes to the “tens” and the pennies to the “ones.” Beginning with the pennies, work through the addition. Explain that when adding money amounts less than a dollar, we must write a cents symbol after each amount. Conclude by referring children to the original example and noting that the only difference between adding money amounts and adding counting numbers is the cents symbol (¢).

You may wish to repeat the activity using other examples that do not require regrouping.