Adding several two-digit numbers · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Adding several two-digit numbers

Mathematics · Addition & Subtraction · ages 7-8
Name ______________________   Date ____________

  1. When adding 23 + 14 + 32, what is a smart first step?

    • Add the ones digits only
    • Split each number into tens and ones
    • Guess the answer

  2. To explain your strategy, you only need to give the final total.

    Circle one:   True   False

  3. Which pair of numbers has ones digits that add up to a multiple of ten?

    • 14 and 23
    • 14 and 26
    • 23 and 26

  4. You need to add 28 + 35 + 42. Which two numbers can you add first to make a friendly multiple of 10?

    • 28 and 42
    • 28 and 35
    • 35 and 42

  5. Sam is adding 16 + 24 + 13 + 25. Which two numbers should he add first to make a round ten?

    • 16 and 24
    • 16 and 13
    • 13 and 25

  6. Which explanation best shows how to solve 12 + 21 + 33 + 14?

    • Add the tens (10+20+30+10=70), then the ones (2+1+3+4=10), then add 70+10=80
    • Just guess a number close to 100
    • Add only the first two numbers and stop

  7. Add 36 + 24 + 18 + 22.

    Answer: ______________

  8. Add just the tens in 15 + 22 + 31 + 14 (that's 10+20+30+10). What do you get?

    1515222231311414

    Answer: ______________

  9. Leo adds 19 + 26 + 31 + 14. He gets tens 10+20+30+10=70 and ones 9+6+1+4=20, then says the total is 80. What mistake did he make?

    • He forgot one of the four numbers
    • He grouped the wrong digits as tens and ones
    • He added 70 + 20 incorrectly; it should be 90

  10. Add 18 + 27 + 32 + 13 by grouping tens and ones. What is the total?

    1818272732321313

    Answer: ______________

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Answer key

For grown-ups. Fold this page away before handing over the rest.

Adding several two-digit numbers W1-mt_TiQbi027PE-s1

  1. Split each number into tens and ones · Splitting into tens and ones turns one big sum into two easier ones.
  2. False · Explaining your strategy means telling which numbers you grouped and how, not just the final total.
  3. 14 and 26 · 4 + 6 = 10, a multiple of ten, so that pair is easy to add first.
  4. 28 and 42 · 28 and 42 make 70, which is a multiple of 10. Then 70 + 35 = 105, and it is easy to add.
  5. 16 and 24 · Their ones digits, 6 and 4, add to 10, so 16 + 24 = 40 exactly.
  6. Add the tens (10+20+30+10=70), then the ones (2+1+3+4=10), then add 70+10=80 · A clear explanation shows each step: the tens total, the ones total, and how you combined them.
  7. 100 · Group the tens and ones. 36 + 24 = 60 and 18 + 22 = 40. Then 60 + 40 = 100.
  8. 70 · 10 + 20 + 30 + 10 = 70.
  9. He added 70 + 20 incorrectly; it should be 90 · 70 + 20 = 90, not 80. Leo's grouping was right, but his last addition step slipped.
  10. 90 · Tens: 10+20+30+10=70. Ones: 8+7+2+3=20. 70+20=90.
Worksheet · LightMySky