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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 730 · 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. 1.645 − 365 =
  2. 2.158 + 528 =
  3. 3.535 + 474 =
  4. 4.707 + 689 =
  5. 5.193 + 248 =
  6. 6.777 + 401 =
  7. 7.589 + 134 =
  8. 8.624 + 673 =
  9. 9.873 − 281 =
  10. 10.887 − 543 =
  11. 11.901 − 157 =
  12. 12.698 + 371 =
  13. 13.941 − 157 =
  14. 14.361 + 338 =
  15. 15.413 + 153 =
  16. 16.783 − 311 =
  17. 17.283 + 243 =
  18. 18.656 + 249 =
  19. 19.701 − 544 =
  20. 20.897 − 185 =
  21. 21.340 + 405 =
  22. 22.650 + 164 =
  23. 23.736 + 299 =
  24. 24.558 + 232 =
  25. 25.569 − 211 =
  26. 26.647 − 414 =
  27. 27.717 + 531 =
  28. 28.639 + 681 =
  29. 29.972 − 661 =
  30. 30.557 − 234 =
  31. 31.327 + 525 =
  32. 32.629 − 274 =
  33. 33.887 − 451 =
  34. 34.474 − 325 =
  35. 35.606 + 686 =
  36. 36.745 + 152 =
  37. 37.544 + 498 =
  38. 38.238 + 395 =
  39. 39.295 + 393 =
  40. 40.620 − 284 =

Answer key

  1. 280
  2. 686
  3. 1009
  4. 1396
  5. 441
  6. 1178
  7. 723
  8. 1297
  9. 592
  10. 344
  11. 744
  12. 1069
  13. 784
  14. 699
  15. 566
  16. 472
  17. 526
  18. 905
  19. 157
  20. 712
  21. 745
  22. 814
  23. 1035
  24. 790
  25. 358
  26. 233
  27. 1248
  28. 1320
  29. 311
  30. 323
  31. 852
  32. 355
  33. 436
  34. 149
  35. 1292
  36. 897
  37. 1042
  38. 633
  39. 688
  40. 336

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