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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 974 · 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. 1.572 + 394 =
  2. 2.707 − 379 =
  3. 3.286 + 428 =
  4. 4.513 + 113 =
  5. 5.242 + 351 =
  6. 6.627 + 404 =
  7. 7.689 + 661 =
  8. 8.706 + 485 =
  9. 9.332 + 159 =
  10. 10.586 + 239 =
  11. 11.285 + 122 =
  12. 12.729 − 606 =
  13. 13.980 − 366 =
  14. 14.821 − 599 =
  15. 15.333 + 644 =
  16. 16.319 + 171 =
  17. 17.797 − 318 =
  18. 18.451 − 343 =
  19. 19.575 − 161 =
  20. 20.547 − 312 =
  21. 21.537 + 646 =
  22. 22.459 + 582 =
  23. 23.812 − 331 =
  24. 24.316 + 223 =
  25. 25.128 + 277 =
  26. 26.690 + 435 =
  27. 27.545 − 179 =
  28. 28.412 + 604 =
  29. 29.482 − 326 =
  30. 30.418 + 551 =
  31. 31.602 + 612 =
  32. 32.762 − 489 =
  33. 33.501 − 356 =
  34. 34.154 + 511 =
  35. 35.125 + 326 =
  36. 36.720 + 457 =
  37. 37.466 − 207 =
  38. 38.533 − 194 =
  39. 39.277 + 563 =
  40. 40.764 + 415 =

Answer key

  1. 966
  2. 328
  3. 714
  4. 626
  5. 593
  6. 1031
  7. 1350
  8. 1191
  9. 491
  10. 825
  11. 407
  12. 123
  13. 614
  14. 222
  15. 977
  16. 490
  17. 479
  18. 108
  19. 414
  20. 235
  21. 1183
  22. 1041
  23. 481
  24. 539
  25. 405
  26. 1125
  27. 366
  28. 1016
  29. 156
  30. 969
  31. 1214
  32. 273
  33. 145
  34. 665
  35. 451
  36. 1177
  37. 259
  38. 339
  39. 840
  40. 1179

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