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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 497 · 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. 1.423 + 174 =
  2. 2.235 + 623 =
  3. 3.556 + 263 =
  4. 4.762 + 337 =
  5. 5.186 + 166 =
  6. 6.787 − 504 =
  7. 7.362 + 236 =
  8. 8.454 − 206 =
  9. 9.625 + 245 =
  10. 10.472 − 206 =
  11. 11.783 − 671 =
  12. 12.739 − 535 =
  13. 13.434 + 641 =
  14. 14.538 − 214 =
  15. 15.281 + 471 =
  16. 16.770 + 176 =
  17. 17.207 + 132 =
  18. 18.207 + 508 =
  19. 19.518 + 154 =
  20. 20.362 + 285 =
  21. 21.462 − 347 =
  22. 22.509 − 345 =
  23. 23.641 + 306 =
  24. 24.522 − 401 =
  25. 25.520 − 417 =
  26. 26.736 − 125 =
  27. 27.157 + 293 =
  28. 28.425 − 244 =
  29. 29.419 − 209 =
  30. 30.967 − 423 =
  31. 31.407 + 436 =
  32. 32.441 + 217 =
  33. 33.558 + 291 =
  34. 34.253 + 524 =
  35. 35.130 + 277 =
  36. 36.701 − 159 =
  37. 37.736 − 536 =
  38. 38.524 + 168 =
  39. 39.614 − 364 =
  40. 40.843 − 124 =

Answer key

  1. 597
  2. 858
  3. 819
  4. 1099
  5. 352
  6. 283
  7. 598
  8. 248
  9. 870
  10. 266
  11. 112
  12. 204
  13. 1075
  14. 324
  15. 752
  16. 946
  17. 339
  18. 715
  19. 672
  20. 647
  21. 115
  22. 164
  23. 947
  24. 121
  25. 103
  26. 611
  27. 450
  28. 181
  29. 210
  30. 544
  31. 843
  32. 658
  33. 849
  34. 777
  35. 407
  36. 542
  37. 200
  38. 692
  39. 250
  40. 719

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