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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 375 · 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. 1.243 + 462 =
  2. 2.207 + 464 =
  3. 3.415 − 254 =
  4. 4.591 − 406 =
  5. 5.419 − 141 =
  6. 6.342 + 576 =
  7. 7.588 + 175 =
  8. 8.639 − 143 =
  9. 9.976 − 761 =
  10. 10.583 + 661 =
  11. 11.692 + 134 =
  12. 12.266 + 251 =
  13. 13.769 − 229 =
  14. 14.532 + 131 =
  15. 15.172 + 253 =
  16. 16.232 + 659 =
  17. 17.430 − 125 =
  18. 18.579 − 455 =
  19. 19.889 − 554 =
  20. 20.581 − 391 =
  21. 21.464 − 344 =
  22. 22.385 + 218 =
  23. 23.707 + 227 =
  24. 24.506 − 191 =
  25. 25.146 + 502 =
  26. 26.505 + 678 =
  27. 27.563 − 227 =
  28. 28.322 + 611 =
  29. 29.470 − 148 =
  30. 30.936 − 385 =
  31. 31.313 + 301 =
  32. 32.649 + 251 =
  33. 33.370 + 117 =
  34. 34.337 + 608 =
  35. 35.516 + 499 =
  36. 36.240 + 537 =
  37. 37.707 − 249 =
  38. 38.602 + 283 =
  39. 39.762 − 209 =
  40. 40.570 − 319 =

Answer key

  1. 705
  2. 671
  3. 161
  4. 185
  5. 278
  6. 918
  7. 763
  8. 496
  9. 215
  10. 1244
  11. 826
  12. 517
  13. 540
  14. 663
  15. 425
  16. 891
  17. 305
  18. 124
  19. 335
  20. 190
  21. 120
  22. 603
  23. 934
  24. 315
  25. 648
  26. 1183
  27. 336
  28. 933
  29. 322
  30. 551
  31. 614
  32. 900
  33. 487
  34. 945
  35. 1015
  36. 777
  37. 458
  38. 885
  39. 553
  40. 251

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