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3-Digit Mental Addition and Subtraction Worksheet

Mental maths lesson 20: Add and subtract 3-digit numbers left to right · Set 597 · 40 questions
TalentJR

How to do it in your head (Hundreds first): Keep the first number as it is and split the second into hundreds, tens and ones. Add (or take away) the hundreds first, then the tens. Finish with the ones — bridge through a ten if you need to.

NameDateTime takenScore ___ / 40
  1. 1.313 + 553 =
  2. 2.733 + 651 =
  3. 3.712 + 512 =
  4. 4.295 + 191 =
  5. 5.674 + 449 =
  6. 6.923 − 193 =
  7. 7.301 + 582 =
  8. 8.944 − 445 =
  9. 9.419 + 115 =
  10. 10.745 + 495 =
  11. 11.629 + 151 =
  12. 12.823 − 207 =
  13. 13.508 − 307 =
  14. 14.263 + 177 =
  15. 15.702 − 223 =
  16. 16.467 − 141 =
  17. 17.798 − 311 =
  18. 18.454 − 155 =
  19. 19.929 − 441 =
  20. 20.232 + 455 =
  21. 21.702 − 598 =
  22. 22.241 + 151 =
  23. 23.475 + 609 =
  24. 24.777 − 535 =
  25. 25.283 + 573 =
  26. 26.688 + 688 =
  27. 27.869 − 419 =
  28. 28.213 + 373 =
  29. 29.528 − 181 =
  30. 30.707 − 245 =
  31. 31.581 + 479 =
  32. 32.862 − 212 =
  33. 33.350 + 673 =
  34. 34.537 + 441 =
  35. 35.471 + 173 =
  36. 36.905 − 197 =
  37. 37.677 + 175 =
  38. 38.557 − 294 =
  39. 39.408 + 539 =
  40. 40.611 + 317 =

Answer key

  1. 866
  2. 1384
  3. 1224
  4. 486
  5. 1123
  6. 730
  7. 883
  8. 499
  9. 534
  10. 1240
  11. 780
  12. 616
  13. 201
  14. 440
  15. 479
  16. 326
  17. 487
  18. 299
  19. 488
  20. 687
  21. 104
  22. 392
  23. 1084
  24. 242
  25. 856
  26. 1376
  27. 450
  28. 586
  29. 347
  30. 462
  31. 1060
  32. 650
  33. 1023
  34. 978
  35. 644
  36. 708
  37. 852
  38. 263
  39. 947
  40. 928

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