This lesson is optional, because the kindergarten standards do not require students to fill in equations with one unknown addend. This lesson does give students more practice with finding the number that makes 10 when added to a given number.

Students have access to tools used throughout the year, including two-color counters, connecting cubes, fingers, 10-frames, and bead tools, to help them find the number that makes 10. With repeated experience, students may know some of the numbers needed to make 10 by memory, such as 5 and 5 or 9 and 1. Students fill in equations to represent these compositions and decompositions of 10.

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