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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 808 · 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. 1.464 − 306 =
  2. 2.829 − 241 =
  3. 3.724 − 299 =
  4. 4.486 + 629 =
  5. 5.240 + 392 =
  6. 6.696 + 211 =
  7. 7.461 + 674 =
  8. 8.514 + 628 =
  9. 9.765 + 351 =
  10. 10.646 + 202 =
  11. 11.488 + 128 =
  12. 12.485 − 239 =
  13. 13.469 + 658 =
  14. 14.207 + 121 =
  15. 15.757 + 226 =
  16. 16.526 − 353 =
  17. 17.274 + 386 =
  18. 18.689 − 122 =
  19. 19.758 + 672 =
  20. 20.636 − 358 =
  21. 21.448 − 242 =
  22. 22.690 + 487 =
  23. 23.498 − 281 =
  24. 24.854 − 724 =
  25. 25.328 + 205 =
  26. 26.483 + 244 =
  27. 27.468 + 519 =
  28. 28.175 + 624 =
  29. 29.557 + 271 =
  30. 30.609 − 417 =
  31. 31.200 + 326 =
  32. 32.603 + 326 =
  33. 33.151 + 336 =
  34. 34.373 + 624 =
  35. 35.462 + 431 =
  36. 36.647 − 502 =
  37. 37.606 − 339 =
  38. 38.893 − 595 =
  39. 39.806 − 431 =
  40. 40.309 + 631 =

Answer key

  1. 158
  2. 588
  3. 425
  4. 1115
  5. 632
  6. 907
  7. 1135
  8. 1142
  9. 1116
  10. 848
  11. 616
  12. 246
  13. 1127
  14. 328
  15. 983
  16. 173
  17. 660
  18. 567
  19. 1430
  20. 278
  21. 206
  22. 1177
  23. 217
  24. 130
  25. 533
  26. 727
  27. 987
  28. 799
  29. 828
  30. 192
  31. 526
  32. 929
  33. 487
  34. 997
  35. 893
  36. 145
  37. 267
  38. 298
  39. 375
  40. 940

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