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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 124 · 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. 1.548 − 124 =
  2. 2.251 + 609 =
  3. 3.294 + 643 =
  4. 4.710 − 265 =
  5. 5.431 − 221 =
  6. 6.370 + 199 =
  7. 7.344 + 223 =
  8. 8.662 − 422 =
  9. 9.238 + 624 =
  10. 10.155 + 116 =
  11. 11.915 − 428 =
  12. 12.719 − 131 =
  13. 13.412 − 266 =
  14. 14.486 − 244 =
  15. 15.905 − 431 =
  16. 16.263 + 653 =
  17. 17.962 − 176 =
  18. 18.492 − 267 =
  19. 19.561 + 334 =
  20. 20.609 − 351 =
  21. 21.134 + 458 =
  22. 22.737 + 307 =
  23. 23.423 + 289 =
  24. 24.721 + 543 =
  25. 25.431 − 283 =
  26. 26.284 + 331 =
  27. 27.480 − 376 =
  28. 28.412 − 134 =
  29. 29.725 + 327 =
  30. 30.663 − 136 =
  31. 31.423 + 631 =
  32. 32.822 − 323 =
  33. 33.420 + 601 =
  34. 34.430 − 172 =
  35. 35.972 − 344 =
  36. 36.439 + 441 =
  37. 37.518 − 151 =
  38. 38.506 − 361 =
  39. 39.149 + 471 =
  40. 40.188 + 174 =

Answer key

  1. 424
  2. 860
  3. 937
  4. 445
  5. 210
  6. 569
  7. 567
  8. 240
  9. 862
  10. 271
  11. 487
  12. 588
  13. 146
  14. 242
  15. 474
  16. 916
  17. 786
  18. 225
  19. 895
  20. 258
  21. 592
  22. 1044
  23. 712
  24. 1264
  25. 148
  26. 615
  27. 104
  28. 278
  29. 1052
  30. 527
  31. 1054
  32. 499
  33. 1021
  34. 258
  35. 628
  36. 880
  37. 367
  38. 145
  39. 620
  40. 362

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