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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 111 · 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. 1.547 + 378 =
  2. 2.497 − 148 =
  3. 3.314 + 491 =
  4. 4.726 − 474 =
  5. 5.735 + 617 =
  6. 6.544 + 383 =
  7. 7.626 + 253 =
  8. 8.454 + 375 =
  9. 9.236 + 659 =
  10. 10.419 + 261 =
  11. 11.528 + 554 =
  12. 12.899 − 794 =
  13. 13.407 + 578 =
  14. 14.504 − 118 =
  15. 15.132 + 392 =
  16. 16.673 + 306 =
  17. 17.753 + 371 =
  18. 18.640 − 386 =
  19. 19.457 + 218 =
  20. 20.711 − 522 =
  21. 21.759 + 516 =
  22. 22.263 + 456 =
  23. 23.214 + 205 =
  24. 24.653 + 199 =
  25. 25.595 + 121 =
  26. 26.535 − 239 =
  27. 27.951 − 258 =
  28. 28.639 − 306 =
  29. 29.631 + 305 =
  30. 30.633 + 469 =
  31. 31.978 − 783 =
  32. 32.892 − 165 =
  33. 33.653 − 445 =
  34. 34.700 + 397 =
  35. 35.562 − 226 =
  36. 36.765 − 142 =
  37. 37.869 − 522 =
  38. 38.482 + 372 =
  39. 39.618 − 489 =
  40. 40.457 − 195 =

Answer key

  1. 925
  2. 349
  3. 805
  4. 252
  5. 1352
  6. 927
  7. 879
  8. 829
  9. 895
  10. 680
  11. 1082
  12. 105
  13. 985
  14. 386
  15. 524
  16. 979
  17. 1124
  18. 254
  19. 675
  20. 189
  21. 1275
  22. 719
  23. 419
  24. 852
  25. 716
  26. 296
  27. 693
  28. 333
  29. 936
  30. 1102
  31. 195
  32. 727
  33. 208
  34. 1097
  35. 336
  36. 623
  37. 347
  38. 854
  39. 129
  40. 262

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