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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 427 · 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. 1.284 + 204 =
  2. 2.363 + 344 =
  3. 3.462 − 173 =
  4. 4.530 − 225 =
  5. 5.488 − 137 =
  6. 6.154 + 131 =
  7. 7.538 − 308 =
  8. 8.775 − 169 =
  9. 9.259 + 185 =
  10. 10.664 − 309 =
  11. 11.601 + 307 =
  12. 12.341 + 688 =
  13. 13.436 + 274 =
  14. 14.963 − 675 =
  15. 15.520 + 112 =
  16. 16.778 + 203 =
  17. 17.202 + 638 =
  18. 18.494 − 138 =
  19. 19.471 − 308 =
  20. 20.295 + 197 =
  21. 21.753 + 552 =
  22. 22.487 + 252 =
  23. 23.445 + 414 =
  24. 24.490 − 371 =
  25. 25.593 − 161 =
  26. 26.898 − 683 =
  27. 27.506 − 158 =
  28. 28.420 − 289 =
  29. 29.480 + 383 =
  30. 30.750 − 539 =
  31. 31.663 + 575 =
  32. 32.839 − 538 =
  33. 33.342 + 503 =
  34. 34.959 − 357 =
  35. 35.603 − 187 =
  36. 36.678 + 593 =
  37. 37.365 + 523 =
  38. 38.707 − 392 =
  39. 39.204 + 195 =
  40. 40.224 + 498 =

Answer key

  1. 488
  2. 707
  3. 289
  4. 305
  5. 351
  6. 285
  7. 230
  8. 606
  9. 444
  10. 355
  11. 908
  12. 1029
  13. 710
  14. 288
  15. 632
  16. 981
  17. 840
  18. 356
  19. 163
  20. 492
  21. 1305
  22. 739
  23. 859
  24. 119
  25. 432
  26. 215
  27. 348
  28. 131
  29. 863
  30. 211
  31. 1238
  32. 301
  33. 845
  34. 602
  35. 416
  36. 1271
  37. 888
  38. 315
  39. 399
  40. 722

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