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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 15 · 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. 1.734 + 237 =
  2. 2.693 + 179 =
  3. 3.471 − 136 =
  4. 4.216 + 121 =
  5. 5.430 − 258 =
  6. 6.987 − 811 =
  7. 7.574 + 531 =
  8. 8.587 − 141 =
  9. 9.575 − 259 =
  10. 10.793 − 309 =
  11. 11.755 − 435 =
  12. 12.753 − 451 =
  13. 13.598 + 213 =
  14. 14.283 + 529 =
  15. 15.340 + 238 =
  16. 16.137 + 529 =
  17. 17.699 − 349 =
  18. 18.531 + 504 =
  19. 19.702 + 565 =
  20. 20.892 − 231 =
  21. 21.231 + 668 =
  22. 22.786 − 361 =
  23. 23.860 − 314 =
  24. 24.568 − 158 =
  25. 25.344 + 328 =
  26. 26.492 + 455 =
  27. 27.558 − 351 =
  28. 28.520 − 148 =
  29. 29.560 + 112 =
  30. 30.655 + 124 =
  31. 31.901 − 493 =
  32. 32.243 + 589 =
  33. 33.648 − 418 =
  34. 34.343 + 264 =
  35. 35.274 + 205 =
  36. 36.514 + 597 =
  37. 37.198 + 139 =
  38. 38.643 − 532 =
  39. 39.670 + 409 =
  40. 40.774 − 113 =

Answer key

  1. 971
  2. 872
  3. 335
  4. 337
  5. 172
  6. 176
  7. 1105
  8. 446
  9. 316
  10. 484
  11. 320
  12. 302
  13. 811
  14. 812
  15. 578
  16. 666
  17. 350
  18. 1035
  19. 1267
  20. 661
  21. 899
  22. 425
  23. 546
  24. 410
  25. 672
  26. 947
  27. 207
  28. 372
  29. 672
  30. 779
  31. 408
  32. 832
  33. 230
  34. 607
  35. 479
  36. 1111
  37. 337
  38. 111
  39. 1079
  40. 661

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