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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 122 · 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. 1.432 − 187 =
  2. 2.251 + 379 =
  3. 3.429 − 135 =
  4. 4.651 − 226 =
  5. 5.630 − 166 =
  6. 6.665 + 325 =
  7. 7.324 + 225 =
  8. 8.837 − 159 =
  9. 9.481 − 267 =
  10. 10.175 + 279 =
  11. 11.518 + 169 =
  12. 12.865 − 169 =
  13. 13.578 + 135 =
  14. 14.914 − 343 =
  15. 15.736 − 572 =
  16. 16.392 + 501 =
  17. 17.591 + 645 =
  18. 18.873 − 186 =
  19. 19.125 + 453 =
  20. 20.739 − 186 =
  21. 21.608 − 283 =
  22. 22.160 + 646 =
  23. 23.887 − 237 =
  24. 24.849 − 217 =
  25. 25.496 + 642 =
  26. 26.167 + 518 =
  27. 27.211 + 237 =
  28. 28.655 + 309 =
  29. 29.376 + 535 =
  30. 30.732 + 345 =
  31. 31.329 + 519 =
  32. 32.431 + 675 =
  33. 33.335 + 677 =
  34. 34.989 − 501 =
  35. 35.733 + 258 =
  36. 36.637 + 433 =
  37. 37.587 − 332 =
  38. 38.332 + 547 =
  39. 39.783 + 252 =
  40. 40.757 − 324 =

Answer key

  1. 245
  2. 630
  3. 294
  4. 425
  5. 464
  6. 990
  7. 549
  8. 678
  9. 214
  10. 454
  11. 687
  12. 696
  13. 713
  14. 571
  15. 164
  16. 893
  17. 1236
  18. 687
  19. 578
  20. 553
  21. 325
  22. 806
  23. 650
  24. 632
  25. 1138
  26. 685
  27. 448
  28. 964
  29. 911
  30. 1077
  31. 848
  32. 1106
  33. 1012
  34. 488
  35. 991
  36. 1070
  37. 255
  38. 879
  39. 1035
  40. 433

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