Lesson 18

The purpose of this lesson is for students to find all of the compositions and decompositions of 10 in the context of a story problem.

In a previous unit, students found more than one solution to Put Together/Take Apart, Both Addends Unknown story problems. In a previous lesson, students used objects, images, and equations to make and break apart 10.

In this lesson, students solve a Put Together/Take Apart, Both Addends Unknown story problem with a total of 10. Then students work together to find all of the solutions to a Put Together/Take Apart, Both Addends Unknown story problem with a total of 10. Students may notice patterns in the solutions, such as that when one addend increases the other addend decreases, to help them determine if they have found all of the solutions. This lesson is optional because the standards do not require students to find all of the solutions for Put Together/Take Apart, Both Addends Unknown story problems.

If students need additional support with the concepts in this lesson, refer back to Unit 5, Section C in the curriculum materials.

• Students can use their bead tool from a previous lesson.

• Students can use their bead tool from a previous lesson.
• Create a chart displaying solutions to be used during the lesson synthesis.

  pigeons in the fountain	pigeons on the bench
  9 8 7 6 5 4 3 2 1	1 2 3 4 5 6 7 8 9

• Gather materials from:
  • Shake and Spill
  • Number Race
  • Grab and Count
  • What's Behind My Back?
  • Pattern Blocks

As students worked together today, where did you see evidence of the mathematical community established over the course of the school year?