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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 913 · 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. 1.686 + 449 =
  2. 2.506 + 248 =
  3. 3.434 − 175 =
  4. 4.927 − 117 =
  5. 5.489 − 233 =
  6. 6.737 − 437 =
  7. 7.675 − 533 =
  8. 8.727 − 166 =
  9. 9.713 − 609 =
  10. 10.450 − 221 =
  11. 11.187 + 388 =
  12. 12.375 + 541 =
  13. 13.294 + 575 =
  14. 14.130 + 321 =
  15. 15.649 − 185 =
  16. 16.489 + 392 =
  17. 17.434 − 281 =
  18. 18.719 − 127 =
  19. 19.428 + 167 =
  20. 20.653 + 331 =
  21. 21.525 − 328 =
  22. 22.514 + 206 =
  23. 23.783 − 428 =
  24. 24.257 + 151 =
  25. 25.873 − 355 =
  26. 26.615 − 258 =
  27. 27.509 − 342 =
  28. 28.501 − 347 =
  29. 29.679 + 474 =
  30. 30.474 − 191 =
  31. 31.776 − 341 =
  32. 32.511 + 612 =
  33. 33.609 − 188 =
  34. 34.137 + 572 =
  35. 35.978 − 516 =
  36. 36.806 − 119 =
  37. 37.676 − 421 =
  38. 38.728 + 268 =
  39. 39.644 + 436 =
  40. 40.700 + 469 =

Answer key

  1. 1135
  2. 754
  3. 259
  4. 810
  5. 256
  6. 300
  7. 142
  8. 561
  9. 104
  10. 229
  11. 575
  12. 916
  13. 869
  14. 451
  15. 464
  16. 881
  17. 153
  18. 592
  19. 595
  20. 984
  21. 197
  22. 720
  23. 355
  24. 408
  25. 518
  26. 357
  27. 167
  28. 154
  29. 1153
  30. 283
  31. 435
  32. 1123
  33. 421
  34. 709
  35. 462
  36. 687
  37. 255
  38. 996
  39. 1080
  40. 1169

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