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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 940 · 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. 1.623 − 393 =
  2. 2.771 − 555 =
  3. 3.199 + 336 =
  4. 4.362 + 124 =
  5. 5.279 + 464 =
  6. 6.715 − 472 =
  7. 7.204 + 218 =
  8. 8.619 + 271 =
  9. 9.254 + 552 =
  10. 10.208 + 502 =
  11. 11.582 + 456 =
  12. 12.347 + 303 =
  13. 13.443 + 574 =
  14. 14.728 + 411 =
  15. 15.488 + 346 =
  16. 16.485 − 199 =
  17. 17.659 − 216 =
  18. 18.613 − 455 =
  19. 19.494 − 356 =
  20. 20.217 + 178 =
  21. 21.226 + 355 =
  22. 22.616 − 235 =
  23. 23.969 − 357 =
  24. 24.573 − 112 =
  25. 25.744 − 603 =
  26. 26.718 + 152 =
  27. 27.320 + 412 =
  28. 28.549 − 308 =
  29. 29.440 − 276 =
  30. 30.448 − 259 =
  31. 31.668 + 386 =
  32. 32.671 − 249 =
  33. 33.707 + 171 =
  34. 34.621 + 265 =
  35. 35.660 + 556 =
  36. 36.573 − 455 =
  37. 37.749 + 363 =
  38. 38.624 + 266 =
  39. 39.652 − 183 =
  40. 40.753 + 265 =

Answer key

  1. 230
  2. 216
  3. 535
  4. 486
  5. 743
  6. 243
  7. 422
  8. 890
  9. 806
  10. 710
  11. 1038
  12. 650
  13. 1017
  14. 1139
  15. 834
  16. 286
  17. 443
  18. 158
  19. 138
  20. 395
  21. 581
  22. 381
  23. 612
  24. 461
  25. 141
  26. 870
  27. 732
  28. 241
  29. 164
  30. 189
  31. 1054
  32. 422
  33. 878
  34. 886
  35. 1216
  36. 118
  37. 1112
  38. 890
  39. 469
  40. 1018

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