Elementary (Grades 2nd – 4th) Mathematics Lesson

Making Tens

Submitted by: Ann Brucker, Ponderosa Elementary, BillingsPublic Schools

Objective: Students will identify and practice adding the combinations of addends that sum to 10.

Materials: Enough of the following supplies for each student:

Unifix cubes—10 cubes of each of six colors

Markers or crayons in the same 6 colors as the Unifix cubes

Sentence Strips

Procedures

  1. Give students time to explore the Unifix cubes. When you notice someone grouping and connecting them by colors, draw attention to it, and ask that the whole class do the same thing, so that everyone ends up with “towers” like this:
  1. Ask students what they notice about the towers. Guide them toward the fact that all of the towers have 10 cubes. Hold up one of the towers and ask students to confirm that there are 10 cubes in it, then break it into two pieces:

Are there still 10 cubes? Put it back together and try breaking it apart in another place. Are there still 10 cubes? Will there still be 10 cubes no matter how you break it (into 2 pieces)?

  1. Challenge students to find all of the different ways to break their ten-towers into two pieces. Example:
  1. If no one discovers it, invite students to arrange their towers into an “interesting way;” guide them toward this arrangement:
  1. Ask students again how many cubes there are of each color; be sure they still agree that there are 10. Invite them to share interesting things that they notice about the pattern made by the configuration they have. Ask them why the ten-towers made such an interesting arrangement and pattern. If no one offers or discovers it, guide them toward understanding that these are the pairs that make 10.
  1. Give each student a sentence strip and the markers. Fold the sentence strip in half to find the center. Model the process as you make a number line with colors that match the towers, starting with the pairs of five:

Students may need guidance in understanding that the 10 tower does have a “partner” in zero.

(note: I only include 1 of the 5s because I want them to see it as a number line—you may need to adapt this at your discretion, including both 5s.)

  1. Monitor students as they create their own 10-pair number lines. (Their colors will probably be different than yours, unless you specifically request that they reconstruct their 10-towers and decompose them to look like the model. The value in this could be that you would always be able to remind them that the “red pair” or the “blue pair” always make 10 the same way… Again, adapt at your discretion.)
  1. Ask students what they notice about their number line. Guide them to recall that the matching colors, which correspond to their matching towers, are pairs of addends that have a sum of 10.
  1. Using their 10-pair number lines, have them complete number sentences by saying “10 is 1 and what?” “10 is 4 and what?” etc., and “2 and what equals 10?” “What and 7 equals 10?”
  1. Practice over a couple of lessons/class periods/days. Follow with the 4-Round activities from Knowing Mathematics, starting on Lesson 1-6.