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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 355 · 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. 1.625 + 362 =
  2. 2.555 − 378 =
  3. 3.596 + 188 =
  4. 4.663 + 136 =
  5. 5.172 + 169 =
  6. 6.695 − 568 =
  7. 7.766 + 153 =
  8. 8.370 + 409 =
  9. 9.556 + 362 =
  10. 10.714 − 306 =
  11. 11.970 − 192 =
  12. 12.814 − 179 =
  13. 13.545 − 141 =
  14. 14.136 + 239 =
  15. 15.539 − 157 =
  16. 16.676 + 544 =
  17. 17.771 + 497 =
  18. 18.219 + 672 =
  19. 19.464 − 272 =
  20. 20.928 − 591 =
  21. 21.441 − 168 =
  22. 22.453 − 163 =
  23. 23.532 − 428 =
  24. 24.644 − 347 =
  25. 25.865 − 686 =
  26. 26.754 + 211 =
  27. 27.753 − 475 =
  28. 28.444 − 341 =
  29. 29.741 + 184 =
  30. 30.472 − 275 =
  31. 31.580 − 131 =
  32. 32.543 − 278 =
  33. 33.366 + 337 =
  34. 34.386 + 241 =
  35. 35.370 + 465 =
  36. 36.707 + 511 =
  37. 37.236 + 215 =
  38. 38.475 − 154 =
  39. 39.160 + 463 =
  40. 40.482 − 363 =

Answer key

  1. 987
  2. 177
  3. 784
  4. 799
  5. 341
  6. 127
  7. 919
  8. 779
  9. 918
  10. 408
  11. 778
  12. 635
  13. 404
  14. 375
  15. 382
  16. 1220
  17. 1268
  18. 891
  19. 192
  20. 337
  21. 273
  22. 290
  23. 104
  24. 297
  25. 179
  26. 965
  27. 278
  28. 103
  29. 925
  30. 197
  31. 449
  32. 265
  33. 703
  34. 627
  35. 835
  36. 1218
  37. 451
  38. 321
  39. 623
  40. 119

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