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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 503 · 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. 1.255 + 586 =
  2. 2.522 + 663 =
  3. 3.757 + 386 =
  4. 4.522 + 148 =
  5. 5.956 − 401 =
  6. 6.678 + 647 =
  7. 7.352 + 469 =
  8. 8.794 − 262 =
  9. 9.872 − 242 =
  10. 10.886 − 302 =
  11. 11.465 + 125 =
  12. 12.604 − 125 =
  13. 13.187 + 143 =
  14. 14.599 + 552 =
  15. 15.602 − 366 =
  16. 16.677 − 221 =
  17. 17.282 + 129 =
  18. 18.462 − 193 =
  19. 19.772 + 151 =
  20. 20.552 − 271 =
  21. 21.467 + 216 =
  22. 22.852 − 513 =
  23. 23.649 − 245 =
  24. 24.912 − 748 =
  25. 25.502 − 373 =
  26. 26.987 − 767 =
  27. 27.757 − 421 =
  28. 28.688 + 629 =
  29. 29.452 − 136 =
  30. 30.577 + 542 =
  31. 31.333 + 126 =
  32. 32.872 − 173 =
  33. 33.853 − 371 =
  34. 34.736 + 451 =
  35. 35.503 + 188 =
  36. 36.695 + 379 =
  37. 37.554 − 174 =
  38. 38.361 + 548 =
  39. 39.737 + 491 =
  40. 40.834 − 691 =

Answer key

  1. 841
  2. 1185
  3. 1143
  4. 670
  5. 555
  6. 1325
  7. 821
  8. 532
  9. 630
  10. 584
  11. 590
  12. 479
  13. 330
  14. 1151
  15. 236
  16. 456
  17. 411
  18. 269
  19. 923
  20. 281
  21. 683
  22. 339
  23. 404
  24. 164
  25. 129
  26. 220
  27. 336
  28. 1317
  29. 316
  30. 1119
  31. 459
  32. 699
  33. 482
  34. 1187
  35. 691
  36. 1074
  37. 380
  38. 909
  39. 1228
  40. 143

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