Lesson 2

In Twos, Threes, and More

Est. Class Sessions: 3

Daily Practice and Problems

Teacher Notes
X

TIMS Bit

Use this bit to review the facts in Group 4.

Ask students to describe the strategies they used to solve these problems. Possible strategies include making tens, thinking addition, and using related facts. Knowing 10 − 3 = 7 helps solve 9 − 3 = 6. Knowing 10 − 2 = 8 helps solve 100 − 20 = 80. Class discussion can help students choose efficient strategies.

  1. 3
  2. 4
  3. 2
  4. 7
  5. 8
  6. 6
  7. 80
  8. 70
  9. 3
  1. I know that 10 − 2 = 8, so 100 − 20 = 80.

G. Subtraction: Making Tens

Use mental math to solve these problems. Write only the answers.

  1. 10 − 7 =
  2. = 11 − 7
  3. 9 − 7 =
  4. 10 − 3 =
  5. = 11 − 3
  6. = 9 − 3
  7. 100 − 20 =
  8. 90 − 20 =
  9. = 9 − 6
  1. Show or tell how you solved 100 − 20.