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Cogito

Grade 1 Math · Chapter 5 · Lesson 5

Answer Key

Counting On or Making Ten?

Two good ways. Which is quicker here?

10 problems · about 12 minutes · 1.OA.C.6

What this lesson teaches

The child solves the same problems both ways and decides which strategy suits the numbers.

  • Counting on suits a small second number.
  • Making ten suits a big one.
  • Both are correct. Pick the quicker one.

Warm-Up Review

From earlier lessons. Loosen up before the new work.

4 problems

  1. Review — Start With the Bigger One: 6 + 9 = ?

    Answer 15

    Why 9 + 6 = 10 + 5 = 15.

  2. Review — Making Ten From Eight: 8 + 5 = ?

    Answer 13

    Why 8 + 5 = 10 + 3 = 13.

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

    Answer 14

    Why 9 + 5 = 10 + 4 = 14.

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

    Answer 15

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

Warm Up

Straightforward practice. Get the method working first.

3 problems

  1. 8 + 2 = ?

    Answer 10

    Why 8 + 2 = 10.

  2. 9 + 6 = ?

    Answer 15

    Why 9 + 6 = 10 + 5 = 15.

  3. 9 + 1 = ?

    Answer 10

    Why One hop. Just count on.

Build It Up

The same ideas with more to keep track of.

1 problem

  1. 8 + 7 = ?

    Answer 15

    Why Make a ten. 10 + 5.

Stretch Yourself

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

2 problems

  1. 9 + 3 = ?

    Answer 12

    Why Either way works here.

  2. Choosing a Way: Which would you rather do for 9 + 8?

    Answer Make a ten.

    Why Making ten turns it into 10 + 7 straight away.