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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 150 · 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. 1.262 + 645 =
  2. 2.496 − 204 =
  3. 3.684 + 262 =
  4. 4.984 − 323 =
  5. 5.525 − 195 =
  6. 6.435 − 181 =
  7. 7.207 + 285 =
  8. 8.591 − 148 =
  9. 9.628 − 321 =
  10. 10.656 − 342 =
  11. 11.603 + 164 =
  12. 12.302 + 339 =
  13. 13.949 − 726 =
  14. 14.717 − 158 =
  15. 15.476 + 345 =
  16. 16.761 + 281 =
  17. 17.716 − 565 =
  18. 18.866 − 377 =
  19. 19.585 + 465 =
  20. 20.417 − 226 =
  21. 21.687 − 137 =
  22. 22.151 + 261 =
  23. 23.717 + 448 =
  24. 24.455 + 224 =
  25. 25.902 − 323 =
  26. 26.244 + 643 =
  27. 27.183 + 161 =
  28. 28.594 − 224 =
  29. 29.715 + 554 =
  30. 30.675 + 424 =
  31. 31.941 − 499 =
  32. 32.947 − 641 =
  33. 33.482 + 181 =
  34. 34.432 − 171 =
  35. 35.431 + 662 =
  36. 36.453 − 312 =
  37. 37.818 − 685 =
  38. 38.153 + 426 =
  39. 39.525 − 389 =
  40. 40.146 + 611 =

Answer key

  1. 907
  2. 292
  3. 946
  4. 661
  5. 330
  6. 254
  7. 492
  8. 443
  9. 307
  10. 314
  11. 767
  12. 641
  13. 223
  14. 559
  15. 821
  16. 1042
  17. 151
  18. 489
  19. 1050
  20. 191
  21. 550
  22. 412
  23. 1165
  24. 679
  25. 579
  26. 887
  27. 344
  28. 370
  29. 1269
  30. 1099
  31. 442
  32. 306
  33. 663
  34. 261
  35. 1093
  36. 141
  37. 133
  38. 579
  39. 136
  40. 757

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