Lesson 22

The purpose of this lesson is for students to subtract from a teen number.

In previous lessons, students learned about the unit of ten and composed and decomposed teen numbers. They also subtracted one-digit numbers from teen numbers without decomposing a ten. The purpose of this lesson is for students to subtract from teen numbers with decomposing a ten. Students may use methods such as take away or relating subtraction to addition. The first activity invites students to solve a Take From, Result Unknown story problem in a way that makes sense to them. In the second activity, students play a game in which they subtract a number 1-9 from a teen number. The lesson synthesis focuses on taking away and counting on as methods for solving subtraction. These methods will be discussed further in the next lesson.

• Each group of 2 needs a set of Number Cards 0–10 and a set of Number Cards 11–20 used in a previous lesson.

As you move into a section that focuses on different subtraction methods, how can you continue to develop students' understanding of the relationship between addition and subtraction and encourage students to work flexibly with both operations?