Mentally adding and subtracting ones with 3-digit numbers · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Adding and subtracting ones from a big number

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

  1. What is 462 − 5?

    Answer: ______________

  2. What is 345 + 7?

    • 342
    • 352
    • 351
    • 355

  3. What is 412 + 6?

    • 418
    • 416
    • 428

  4. True or false: when you add or subtract a small number, the hundreds digit almost always stays the same.

    Circle one:   True   False

  5. What is 500 − 6?

    Answer: ______________

  6. Leo has 523 stickers. He gets 8 more. How many stickers does he have now?

    Answer: ______________

  7. What is 238 + 6?

    • 234
    • 248
    • 244
    • 243

  8. Fred says 238 + 6 = 234. Is Fred right?

    Circle one:   True   False

  9. Ivy computed 274 + 9 and wrote 273, only changing the ones digit. What did she forget to do?

    • Add the ones digits correctly
    • Carry the extra ten into the tens place
    • Keep the hundreds digit the same

  10. What is 300 − 7?

    Answer: ______________

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Answer key

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

Adding and subtracting ones from a big number W1-mt_oDU_8zMZjp-s1

  1. 457 · Taking 5 from the 2 ones borrows a ten: 462 − 5 = 457.
  2. 352 · Adding 7 to the 5 ones crosses into the next ten: 345 + 7 = 352.
  3. 418 · 412 + 6: only the ones digit changes. 2 + 6 = 8, so 412 becomes 418.
  4. True · The hundreds digit is far from the ones place, so it almost never changes when you add or subtract a small number.
  5. 494 · Taking 6 from an empty ones place breaks a hundred: 500 − 6 = 494.
  6. 531 · 3 + 8 = 11, so the ones become 1 and the tens go up by one: 523 + 8 = 531.
  7. 244 · Adding 6 to the 8 ones crosses into the next ten: 238 + 6 = 244.
  8. False · Fred is wrong. Adding 6 grows the total to 244, not 234.
  9. Carry the extra ten into the tens place · 4 + 9 = 13. The ones digit becomes 3, but the extra ten must carry into the tens place, so the real answer is 283, not 273.
  10. 293 · Taking 7 breaks a hundred: 300 − 7 = 293.
Worksheet · LightMySky