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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 431 · 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. 1.465 + 631 =
  2. 2.705 + 305 =
  3. 3.453 + 384 =
  4. 4.823 − 317 =
  5. 5.139 + 176 =
  6. 6.248 + 595 =
  7. 7.594 + 598 =
  8. 8.559 − 277 =
  9. 9.544 + 201 =
  10. 10.843 − 715 =
  11. 11.937 − 235 =
  12. 12.654 − 257 =
  13. 13.645 + 283 =
  14. 14.979 − 551 =
  15. 15.169 + 447 =
  16. 16.814 − 158 =
  17. 17.421 − 304 =
  18. 18.894 − 267 =
  19. 19.416 − 308 =
  20. 20.184 + 275 =
  21. 21.137 + 283 =
  22. 22.215 + 241 =
  23. 23.571 − 317 =
  24. 24.521 − 117 =
  25. 25.267 + 148 =
  26. 26.714 − 161 =
  27. 27.435 − 121 =
  28. 28.733 + 565 =
  29. 29.496 + 229 =
  30. 30.910 − 124 =
  31. 31.470 + 171 =
  32. 32.249 + 204 =
  33. 33.300 + 114 =
  34. 34.158 + 338 =
  35. 35.982 − 123 =
  36. 36.468 − 188 =
  37. 37.290 + 159 =
  38. 38.535 − 114 =
  39. 39.547 − 256 =
  40. 40.185 + 501 =

Answer key

  1. 1096
  2. 1010
  3. 837
  4. 506
  5. 315
  6. 843
  7. 1192
  8. 282
  9. 745
  10. 128
  11. 702
  12. 397
  13. 928
  14. 428
  15. 616
  16. 656
  17. 117
  18. 627
  19. 108
  20. 459
  21. 420
  22. 456
  23. 254
  24. 404
  25. 415
  26. 553
  27. 314
  28. 1298
  29. 725
  30. 786
  31. 641
  32. 453
  33. 414
  34. 496
  35. 859
  36. 280
  37. 449
  38. 421
  39. 291
  40. 686

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