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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 456 · 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. 1.567 − 121 =
  2. 2.282 + 528 =
  3. 3.749 + 397 =
  4. 4.766 + 316 =
  5. 5.681 + 686 =
  6. 6.497 − 296 =
  7. 7.930 − 751 =
  8. 8.679 + 624 =
  9. 9.394 + 292 =
  10. 10.621 + 409 =
  11. 11.561 + 485 =
  12. 12.953 − 461 =
  13. 13.792 − 677 =
  14. 14.560 − 192 =
  15. 15.258 + 413 =
  16. 16.575 − 276 =
  17. 17.644 + 383 =
  18. 18.453 − 277 =
  19. 19.750 + 336 =
  20. 20.800 − 478 =
  21. 21.550 + 202 =
  22. 22.477 + 116 =
  23. 23.337 + 161 =
  24. 24.632 − 208 =
  25. 25.776 − 265 =
  26. 26.640 + 634 =
  27. 27.832 − 615 =
  28. 28.617 − 473 =
  29. 29.530 − 171 =
  30. 30.422 + 661 =
  31. 31.521 − 122 =
  32. 32.533 + 442 =
  33. 33.195 + 139 =
  34. 34.164 + 179 =
  35. 35.281 + 275 =
  36. 36.691 + 145 =
  37. 37.269 + 503 =
  38. 38.499 − 138 =
  39. 39.234 + 157 =
  40. 40.486 + 312 =

Answer key

  1. 446
  2. 810
  3. 1146
  4. 1082
  5. 1367
  6. 201
  7. 179
  8. 1303
  9. 686
  10. 1030
  11. 1046
  12. 492
  13. 115
  14. 368
  15. 671
  16. 299
  17. 1027
  18. 176
  19. 1086
  20. 322
  21. 752
  22. 593
  23. 498
  24. 424
  25. 511
  26. 1274
  27. 217
  28. 144
  29. 359
  30. 1083
  31. 399
  32. 975
  33. 334
  34. 343
  35. 556
  36. 836
  37. 772
  38. 361
  39. 391
  40. 798

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