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Cogito

Grade 1 Math · Chapter 5 · Lesson 3

Answer Key

Making Ten From Eight

Now move two across.

10 problems · about 13 minutes · 1.OA.C.6, 1.OA.B.3

What this lesson teaches

The child adds 8 + n by moving two counters to complete the ten, generalising the make-ten move.

  • The make-ten move works from any number.
  • Ask how many more it needs.
  • Take that many from the other number.

Warm-Up Review

From earlier lessons. Loosen up before the new work.

4 problems

  1. Review — Making Ten From Nine: 9 + 5 = ?

    Answer 14

    Why 9 + 5 = 10 + 4 = 14.

  2. Review — Adding Three Numbers: 3 + 7 + 5 = ?

    Answer 15

    Why 3 + 7 = 10, then 10 + 5 = 15.

  3. Review — Counting to Twenty and Back: What comes after 18?

    Answer 19

    Why 19 comes after 18.

  4. Review — One More, One Less to Twenty: One more than 11?

    Answer 12

    Why One more than 11 is 12.

Warm Up

Straightforward practice. Get the method working first.

3 problems

  1. 8 + 5 = ?

    Answer 13

    Why 8 + 5 = 10 + 3 = 13.

  2. 8 + 9 = ?

    Answer 17

    Why 8 + 9 = 10 + 7 = 17.

  3. 8 + 4 = ?

    Answer 12

    Why 10 + 2.

Build It Up

The same ideas with more to keep track of.

1 problem

  1. 8 + 8 = ?

    Answer 16

    Why 10 + 6.

Stretch Yourself

Mixed problems. Work out what kind of question it is before you start.

2 problems

  1. 7 + 5 = ?

    Answer 12

    Why 7 needs 3. 10 + 2.

  2. Bookshelf: There are 8 books on one shelf and 7 on another. How many books in all?

    Answer 15 books

    Why 8 + 7 = 10 + 5 = 15.