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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 999 · 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. 1.510 + 279 =
  2. 2.197 + 258 =
  3. 3.325 + 267 =
  4. 4.726 − 221 =
  5. 5.461 + 184 =
  6. 6.572 − 393 =
  7. 7.668 + 575 =
  8. 8.733 − 277 =
  9. 9.973 − 791 =
  10. 10.474 + 448 =
  11. 11.279 + 178 =
  12. 12.702 − 531 =
  13. 13.398 + 623 =
  14. 14.478 − 341 =
  15. 15.188 + 418 =
  16. 16.299 + 146 =
  17. 17.234 + 114 =
  18. 18.641 + 607 =
  19. 19.761 − 576 =
  20. 20.939 − 121 =
  21. 21.240 + 393 =
  22. 22.913 − 341 =
  23. 23.155 + 367 =
  24. 24.312 + 114 =
  25. 25.623 − 266 =
  26. 26.702 − 169 =
  27. 27.148 + 217 =
  28. 28.787 + 578 =
  29. 29.272 + 621 =
  30. 30.497 − 317 =
  31. 31.658 + 281 =
  32. 32.689 − 511 =
  33. 33.977 − 161 =
  34. 34.162 + 612 =
  35. 35.630 − 481 =
  36. 36.778 + 497 =
  37. 37.522 + 649 =
  38. 38.617 + 236 =
  39. 39.705 + 421 =
  40. 40.747 − 593 =

Answer key

  1. 789
  2. 455
  3. 592
  4. 505
  5. 645
  6. 179
  7. 1243
  8. 456
  9. 182
  10. 922
  11. 457
  12. 171
  13. 1021
  14. 137
  15. 606
  16. 445
  17. 348
  18. 1248
  19. 185
  20. 818
  21. 633
  22. 572
  23. 522
  24. 426
  25. 357
  26. 533
  27. 365
  28. 1365
  29. 893
  30. 180
  31. 939
  32. 178
  33. 816
  34. 774
  35. 149
  36. 1275
  37. 1171
  38. 853
  39. 1126
  40. 154

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