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Cogito

Grade 1 Math · Chapter 2 · Lesson 8

Answer Key

Doubles and One More

Use a double you know to work out one you do not.

10 problems · about 12 minutes · 1.OA.C.6, 1.OA.B.3

What this lesson teaches

The child uses a known double to find a near-double, for example 4 + 5 as 4 + 4 and one more.

  • Some sums are nearly doubles.
  • Use the double you already know.
  • Then add one more.

Warm-Up Review

From earlier lessons. Loosen up before the new work.

5 problems

  1. Review — Doubles: 4 + 4 = ?

    Answer 8

    Why 4 + 4 = 8.

  2. Review — Finding the Missing Part: 5 + ? = 9

    Answer 4

    Why 5 + 4 = 9.

  3. Review — What Does Equals Mean?: What does the equals sign mean?

    Answer Both sides are the same amount.

    Why Equals means the same amount as. That is why 9 = 6 + 3 works too.

  4. Review — Adding in Any Order: 3 + 5 = 8. So what is 5 + 3?

    Answer 8

    Why Swapping the parts never changes the whole.

  5. Review — Counting On With Pictures: Start at 9. Count on 1. Where do you land?

    Answer 10

    Why 9 + 1 = 10.

Warm Up

Straightforward practice. Get the method working first.

3 problems

  1. 3 + 4 = ?

    Answer 7

    Why 3 + 3 = 6, and one more is 7.

  2. 5 + 4 = ?

    Answer 9

    Why 4 + 4 = 8, and one more is 9.

  3. 2 + 3 = ?

    Answer 5

    Why 2 + 2 = 4. One more.

Build It Up

The same ideas with more to keep track of.

1 problem

  1. 4 + 5 = ?

    Answer 9

    Why 4 + 4 = 8. One more.

Stretch Yourself

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

1 problem

  1. Cookie Jar: Mia has 4 cookies. Ben has 5. How many cookies altogether?

    Answer 9 cookies

    Why 4 + 4 = 8, and one more makes 9.