Lesson 8

The purpose of this lesson is for students to solve and represent Put Together/Take Apart, Addend Unknown story problems. 

Students solve in any way that makes sense to them and write equations to match the problems. This work builds on the work students did with other types of Put Together/Take Apart problems in previous lessons. They extend the familiar game, Shake and Spill. As students play the game in this lesson, they know the total and the number of red counters and need to figure out the number of yellow counters. Students write equations to match the context and explain how the equation relates to the problem. The focus in this lesson is on missing addend addition equations, but students may solve or represent the problems using subtraction. Subtraction equations should be accepted and will be the focus of lessons in the next section. When students recognize that a number in an equation represents a specific quantity they reason abstractly and quantitatively (MP2).

• Each group of 2 needs 10 two-color counters and a cup (at least 8 oz).

Are students trying new methods when they hear others during the discussion? How can you encourage students to try new methods?