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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 724 · 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. 1.526 + 324 =
  2. 2.814 − 255 =
  3. 3.190 + 155 =
  4. 4.561 − 341 =
  5. 5.687 − 408 =
  6. 6.215 + 237 =
  7. 7.370 + 631 =
  8. 8.777 − 372 =
  9. 9.182 + 309 =
  10. 10.699 − 364 =
  11. 11.768 − 332 =
  12. 12.461 − 234 =
  13. 13.164 + 296 =
  14. 14.642 − 226 =
  15. 15.136 + 628 =
  16. 16.770 + 122 =
  17. 17.928 − 674 =
  18. 18.702 − 463 =
  19. 19.175 + 339 =
  20. 20.583 + 448 =
  21. 21.206 + 591 =
  22. 22.620 − 154 =
  23. 23.650 − 331 =
  24. 24.989 − 299 =
  25. 25.390 + 554 =
  26. 26.157 + 299 =
  27. 27.526 + 544 =
  28. 28.498 + 281 =
  29. 29.214 + 453 =
  30. 30.790 − 399 =
  31. 31.193 + 281 =
  32. 32.151 + 195 =
  33. 33.901 − 381 =
  34. 34.302 + 231 =
  35. 35.601 − 154 =
  36. 36.364 + 551 =
  37. 37.244 + 143 =
  38. 38.539 − 432 =
  39. 39.321 + 216 =
  40. 40.920 − 594 =

Answer key

  1. 850
  2. 559
  3. 345
  4. 220
  5. 279
  6. 452
  7. 1001
  8. 405
  9. 491
  10. 335
  11. 436
  12. 227
  13. 460
  14. 416
  15. 764
  16. 892
  17. 254
  18. 239
  19. 514
  20. 1031
  21. 797
  22. 466
  23. 319
  24. 690
  25. 944
  26. 456
  27. 1070
  28. 779
  29. 667
  30. 391
  31. 474
  32. 346
  33. 520
  34. 533
  35. 447
  36. 915
  37. 387
  38. 107
  39. 537
  40. 326

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