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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 101 · 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. 1.408 + 314 =
  2. 2.750 − 456 =
  3. 3.210 + 451 =
  4. 4.771 − 166 =
  5. 5.779 + 112 =
  6. 6.124 + 562 =
  7. 7.433 − 137 =
  8. 8.742 + 251 =
  9. 9.651 − 477 =
  10. 10.607 + 455 =
  11. 11.686 + 282 =
  12. 12.221 + 639 =
  13. 13.746 + 139 =
  14. 14.952 − 574 =
  15. 15.250 + 613 =
  16. 16.660 − 241 =
  17. 17.740 − 497 =
  18. 18.894 − 759 =
  19. 19.642 + 149 =
  20. 20.617 − 181 =
  21. 21.420 + 206 =
  22. 22.228 + 656 =
  23. 23.720 + 119 =
  24. 24.286 + 347 =
  25. 25.770 − 635 =
  26. 26.412 − 236 =
  27. 27.605 − 472 =
  28. 28.735 − 234 =
  29. 29.489 + 331 =
  30. 30.667 + 431 =
  31. 31.644 + 469 =
  32. 32.971 − 816 =
  33. 33.491 − 227 =
  34. 34.568 + 208 =
  35. 35.828 − 321 =
  36. 36.214 + 514 =
  37. 37.711 + 482 =
  38. 38.698 − 481 =
  39. 39.571 − 352 =
  40. 40.454 + 635 =

Answer key

  1. 722
  2. 294
  3. 661
  4. 605
  5. 891
  6. 686
  7. 296
  8. 993
  9. 174
  10. 1062
  11. 968
  12. 860
  13. 885
  14. 378
  15. 863
  16. 419
  17. 243
  18. 135
  19. 791
  20. 436
  21. 626
  22. 884
  23. 839
  24. 633
  25. 135
  26. 176
  27. 133
  28. 501
  29. 820
  30. 1098
  31. 1113
  32. 155
  33. 264
  34. 776
  35. 507
  36. 728
  37. 1193
  38. 217
  39. 219
  40. 1089

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