Fluent adding and subtracting within 100 · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Two-digit addition and subtraction, made fast

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

  1. What is 35 + 48?

    Answer: ______________

  2. What is 61 + 28?

    • 79
    • 89
    • 99
    • 81

  3. Break 46 + 37 into tens and ones. What is 40 + 30?

    • 60
    • 70
    • 80

  4. To find 68 + 27, you can round 27 up to 30, work out 68 + 30, then take away the extra 3.

    Circle one:   True   False

  5. True or false: 38 + 25 = 63.

    Circle one:   True   False

  6. 68 + 27: since 27 is so close to 30, which plan takes the fewest steps?

    • Round 27 to 30, add, then fix the extra 3
    • Break 68 and 27 into tens and ones, then add each part
    • Count on from 68 one step at a time until 95

  7. What is 72 - 26?

    Answer: ______________

  8. Ella adds 47 + 26 by using 30 instead of 26. Which plan gives the right total?

    • Add 30 instead of 26, then take away the extra 4
    • Add 30 instead of 26, then add 4 more to the total
    • Add 30 instead of 26, then take away 6 from it

  9. Ben adds 58 + 36. He breaks it into 50+30=80 and 8+6=14, then says 80+14=84. What is his mistake?

    • He broke 58 and 36 into the wrong tens and ones
    • 8+6 should have been 15, not 14
    • He added 80+14 wrong; it should be 94, not 84

  10. You need to find 74 - 38. Pick a strategy and solve it. What is the answer?

    Answer: ______________

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Answer key

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

Two-digit addition and subtraction, made fast W1-mt_cChv2j_-Da-s1

  1. 83 · Add the tens, add the ones, then join the parts.
  2. 89 · Add tens: 60 + 20 = 80. Add ones: 1 + 8 = 9. The total is 89.
  3. 70 · 4 tens plus 3 tens is 7 tens, so 40 + 30 = 70.
  4. True · 68 + 30 = 98. Taking away the extra 3 gives 95, and 68 + 27 is also 95. So the plan works.
  5. True · Add tens with tens and ones with ones, then combine.
  6. Round 27 to 30, add, then fix the extra 3 · Rounding takes two steps: 68 + 30 = 98, then 98 - 3 = 95. Splitting into tens and ones takes three adds, and counting on takes 27 steps.
  7. 46 · Take away 20 to get 52, then take away 6 to get 46.
  8. Add 30 instead of 26, then take away the extra 4 · 30 is 4 more than 26, so adding 30 adds 4 too many. Take the extra 4 away: 77 - 4 = 73.
  9. He added 80+14 wrong; it should be 94, not 84 · 80 + 14 equals 94. Ben's breakdown was right, but he added the last step wrong.
  10. 36 · 74 - 30 = 44, then 44 - 8 = 36. Breaking 38 into 30 and 8 makes it easier.
Worksheet · LightMySky