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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 756 · 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. 1.307 + 179 =
  2. 2.770 + 265 =
  3. 3.764 − 369 =
  4. 4.227 + 276 =
  5. 5.438 + 241 =
  6. 6.158 + 418 =
  7. 7.211 + 449 =
  8. 8.638 + 121 =
  9. 9.813 − 123 =
  10. 10.140 + 318 =
  11. 11.182 + 604 =
  12. 12.423 + 378 =
  13. 13.371 + 186 =
  14. 14.654 − 281 =
  15. 15.546 − 261 =
  16. 16.568 + 206 =
  17. 17.470 − 211 =
  18. 18.915 − 356 =
  19. 19.469 + 576 =
  20. 20.412 − 118 =
  21. 21.786 + 255 =
  22. 22.178 + 645 =
  23. 23.496 − 276 =
  24. 24.596 − 236 =
  25. 25.237 + 413 =
  26. 26.655 + 429 =
  27. 27.454 + 258 =
  28. 28.614 − 443 =
  29. 29.683 + 201 =
  30. 30.459 − 164 =
  31. 31.422 − 124 =
  32. 32.611 + 196 =
  33. 33.974 − 555 =
  34. 34.264 + 441 =
  35. 35.585 + 271 =
  36. 36.873 − 226 =
  37. 37.451 − 215 =
  38. 38.463 + 319 =
  39. 39.408 + 678 =
  40. 40.920 − 553 =

Answer key

  1. 486
  2. 1035
  3. 395
  4. 503
  5. 679
  6. 576
  7. 660
  8. 759
  9. 690
  10. 458
  11. 786
  12. 801
  13. 557
  14. 373
  15. 285
  16. 774
  17. 259
  18. 559
  19. 1045
  20. 294
  21. 1041
  22. 823
  23. 220
  24. 360
  25. 650
  26. 1084
  27. 712
  28. 171
  29. 884
  30. 295
  31. 298
  32. 807
  33. 419
  34. 705
  35. 856
  36. 647
  37. 236
  38. 782
  39. 1086
  40. 367

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