Lesson 21 Compose and Decompose Numbers 11–19

    • Let’s make groups of 10.

Warm-up Which One Doesn’t Belong: Numbers 11–20

Which one doesn’t belong?

  1. a line of 13 dots
  2. a ten frame filled with 5 extra counters below
  3. two hand showing ten fingers
    two hands showing 3 fingers
  4. a group of dost with 10 in a circle and 3 outside of it

Activity 1 Where Will They Sit?

table and 10 chairs
  1. table and 10 chairs

  2. table and 10 chairs

  3. table and 10 chairs


  4. table and 10 chairs


  5. table and 10 chairs


  6. table and 10 chairs


Activity 2 Finish the Equations

Kiran wrote equations to show the total number of students and how many students sat at the table and how many sat on the rug, but he didn’t finish the equations. Finish filling in each equation. You can use connecting cubes or two-color counters if they are helpful.

Activity 3 Centers: Choice Time

Choose a center.

Shake and Spill

Center. Shake and Spill.

Number Race

Center. Number Race.

Grab and Count

Center. Grab and Count.

What’s Behind My Back?

Center. What's Behind My Back.

Pattern Blocks

Center. Pattern Blocks.