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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 785 · 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. 1.665 − 305 =
  2. 2.807 − 254 =
  3. 3.221 + 165 =
  4. 4.671 + 243 =
  5. 5.510 + 688 =
  6. 6.309 + 621 =
  7. 7.381 + 226 =
  8. 8.528 − 409 =
  9. 9.543 + 117 =
  10. 10.589 + 593 =
  11. 11.513 − 384 =
  12. 12.740 − 395 =
  13. 13.481 − 311 =
  14. 14.773 − 243 =
  15. 15.388 + 151 =
  16. 16.539 − 373 =
  17. 17.855 − 681 =
  18. 18.225 + 314 =
  19. 19.234 + 607 =
  20. 20.240 + 545 =
  21. 21.973 − 432 =
  22. 22.379 + 136 =
  23. 23.519 − 231 =
  24. 24.191 + 407 =
  25. 25.510 − 144 =
  26. 26.441 + 522 =
  27. 27.790 − 608 =
  28. 28.525 − 249 =
  29. 29.475 − 242 =
  30. 30.262 + 515 =
  31. 31.307 + 465 =
  32. 32.639 − 311 =
  33. 33.575 − 436 =
  34. 34.748 − 152 =
  35. 35.441 − 203 =
  36. 36.480 + 583 =
  37. 37.211 + 464 =
  38. 38.754 − 141 =
  39. 39.868 − 635 =
  40. 40.601 + 673 =

Answer key

  1. 360
  2. 553
  3. 386
  4. 914
  5. 1198
  6. 930
  7. 607
  8. 119
  9. 660
  10. 1182
  11. 129
  12. 345
  13. 170
  14. 530
  15. 539
  16. 166
  17. 174
  18. 539
  19. 841
  20. 785
  21. 541
  22. 515
  23. 288
  24. 598
  25. 366
  26. 963
  27. 182
  28. 276
  29. 233
  30. 777
  31. 772
  32. 328
  33. 139
  34. 596
  35. 238
  36. 1063
  37. 675
  38. 613
  39. 233
  40. 1274

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