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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 819 · 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. 1.579 + 245 =
  2. 2.913 − 128 =
  3. 3.689 − 523 =
  4. 4.195 + 288 =
  5. 5.645 − 154 =
  6. 6.204 + 205 =
  7. 7.361 + 321 =
  8. 8.282 + 369 =
  9. 9.416 + 661 =
  10. 10.205 + 584 =
  11. 11.737 − 374 =
  12. 12.218 + 186 =
  13. 13.274 + 419 =
  14. 14.907 − 167 =
  15. 15.232 + 516 =
  16. 16.347 + 501 =
  17. 17.831 − 587 =
  18. 18.209 + 261 =
  19. 19.920 − 258 =
  20. 20.684 − 185 =
  21. 21.918 − 696 =
  22. 22.430 − 232 =
  23. 23.436 − 142 =
  24. 24.515 − 381 =
  25. 25.443 + 328 =
  26. 26.273 + 352 =
  27. 27.345 + 127 =
  28. 28.488 − 187 =
  29. 29.163 + 352 =
  30. 30.624 + 434 =
  31. 31.296 + 114 =
  32. 32.390 + 451 =
  33. 33.240 + 563 =
  34. 34.264 + 451 =
  35. 35.422 + 562 =
  36. 36.511 − 112 =
  37. 37.202 + 343 =
  38. 38.353 + 149 =
  39. 39.223 + 208 =
  40. 40.559 + 513 =

Answer key

  1. 824
  2. 785
  3. 166
  4. 483
  5. 491
  6. 409
  7. 682
  8. 651
  9. 1077
  10. 789
  11. 363
  12. 404
  13. 693
  14. 740
  15. 748
  16. 848
  17. 244
  18. 470
  19. 662
  20. 499
  21. 222
  22. 198
  23. 294
  24. 134
  25. 771
  26. 625
  27. 472
  28. 301
  29. 515
  30. 1058
  31. 410
  32. 841
  33. 803
  34. 715
  35. 984
  36. 399
  37. 545
  38. 502
  39. 431
  40. 1072

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