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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 105 · 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. 1.641 + 392 =
  2. 2.521 + 502 =
  3. 3.291 + 309 =
  4. 4.324 + 203 =
  5. 5.780 − 674 =
  6. 6.470 − 158 =
  7. 7.313 + 609 =
  8. 8.729 − 411 =
  9. 9.626 + 501 =
  10. 10.579 − 128 =
  11. 11.798 − 679 =
  12. 12.446 + 296 =
  13. 13.762 − 136 =
  14. 14.320 + 181 =
  15. 15.537 + 441 =
  16. 16.777 + 407 =
  17. 17.747 + 196 =
  18. 18.211 + 191 =
  19. 19.936 − 452 =
  20. 20.684 − 554 =
  21. 21.517 + 381 =
  22. 22.508 − 241 =
  23. 23.422 + 322 =
  24. 24.435 − 153 =
  25. 25.537 + 203 =
  26. 26.594 + 539 =
  27. 27.534 + 213 =
  28. 28.450 − 131 =
  29. 29.236 + 463 =
  30. 30.892 − 277 =
  31. 31.145 + 538 =
  32. 32.494 − 203 =
  33. 33.665 − 516 =
  34. 34.139 + 125 =
  35. 35.901 − 581 =
  36. 36.439 − 128 =
  37. 37.686 + 676 =
  38. 38.501 + 537 =
  39. 39.145 + 164 =
  40. 40.473 + 329 =

Answer key

  1. 1033
  2. 1023
  3. 600
  4. 527
  5. 106
  6. 312
  7. 922
  8. 318
  9. 1127
  10. 451
  11. 119
  12. 742
  13. 626
  14. 501
  15. 978
  16. 1184
  17. 943
  18. 402
  19. 484
  20. 130
  21. 898
  22. 267
  23. 744
  24. 282
  25. 740
  26. 1133
  27. 747
  28. 319
  29. 699
  30. 615
  31. 683
  32. 291
  33. 149
  34. 264
  35. 320
  36. 311
  37. 1362
  38. 1038
  39. 309
  40. 802

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