operations · Year 1 · AC9M1N04

Addition within twenty

When an addition crosses ten, make ten first. Start with the larger number, find how many more make ten, and split the other number into that amount and the rest. Then add the rest to ten. For a missing number, add the jump to ten and the jump from ten.

Sample questions

7 + 4 = ?

  1. Fill the first ten-frame: move 3 counters across from the second frame.
  2. The first frame now holds 10, and 1 is left in the second frame.
  3. 10 + 1 = 11.

Answer: 11

9 + 4 = ?

  1. Fill the first ten-frame: move 1 counter across from the second frame.
  2. The first frame now holds 10, and 3 are left in the second frame.
  3. 10 + 3 = 13.

Answer: 13

7 + 8 = ?

  1. Fill the first ten-frame: move 2 counters across from the second frame.
  2. The first frame now holds 10, and 5 are left in the second frame.
  3. 10 + 5 = 15.

Answer: 15

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