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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 370 · 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. 1.722 + 656 =
  2. 2.249 + 581 =
  3. 3.706 + 455 =
  4. 4.191 + 402 =
  5. 5.646 − 546 =
  6. 6.422 − 283 =
  7. 7.368 + 321 =
  8. 8.423 − 121 =
  9. 9.961 − 212 =
  10. 10.184 + 464 =
  11. 11.652 + 638 =
  12. 12.164 + 666 =
  13. 13.382 + 112 =
  14. 14.541 − 329 =
  15. 15.842 − 137 =
  16. 16.611 + 256 =
  17. 17.506 − 313 =
  18. 18.855 − 686 =
  19. 19.749 − 497 =
  20. 20.751 − 267 =
  21. 21.769 − 261 =
  22. 22.761 + 652 =
  23. 23.451 + 529 =
  24. 24.668 − 282 =
  25. 25.503 + 127 =
  26. 26.493 − 184 =
  27. 27.397 + 453 =
  28. 28.967 − 373 =
  29. 29.416 − 166 =
  30. 30.192 + 514 =
  31. 31.883 − 534 =
  32. 32.531 + 581 =
  33. 33.467 − 219 =
  34. 34.309 + 172 =
  35. 35.668 − 337 =
  36. 36.649 − 281 =
  37. 37.923 − 797 =
  38. 38.403 + 351 =
  39. 39.178 + 392 =
  40. 40.558 − 161 =

Answer key

  1. 1378
  2. 830
  3. 1161
  4. 593
  5. 100
  6. 139
  7. 689
  8. 302
  9. 749
  10. 648
  11. 1290
  12. 830
  13. 494
  14. 212
  15. 705
  16. 867
  17. 193
  18. 169
  19. 252
  20. 484
  21. 508
  22. 1413
  23. 980
  24. 386
  25. 630
  26. 309
  27. 850
  28. 594
  29. 250
  30. 706
  31. 349
  32. 1112
  33. 248
  34. 481
  35. 331
  36. 368
  37. 126
  38. 754
  39. 570
  40. 397

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