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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 480 · 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. 1.446 + 343 =
  2. 2.797 − 354 =
  3. 3.645 + 647 =
  4. 4.715 + 323 =
  5. 5.978 − 715 =
  6. 6.202 + 191 =
  7. 7.235 + 337 =
  8. 8.504 − 205 =
  9. 9.752 + 332 =
  10. 10.433 + 496 =
  11. 11.521 − 149 =
  12. 12.162 + 287 =
  13. 13.634 + 654 =
  14. 14.777 + 152 =
  15. 15.426 − 152 =
  16. 16.702 + 445 =
  17. 17.529 − 318 =
  18. 18.504 + 662 =
  19. 19.507 − 318 =
  20. 20.989 − 366 =
  21. 21.594 − 297 =
  22. 22.951 − 411 =
  23. 23.537 + 404 =
  24. 24.466 − 365 =
  25. 25.663 − 341 =
  26. 26.752 + 123 =
  27. 27.660 − 493 =
  28. 28.367 + 678 =
  29. 29.486 + 226 =
  30. 30.199 + 577 =
  31. 31.399 + 578 =
  32. 32.622 + 332 =
  33. 33.686 − 381 =
  34. 34.441 + 123 =
  35. 35.557 + 157 =
  36. 36.960 − 329 =
  37. 37.596 + 324 =
  38. 38.869 − 331 =
  39. 39.376 + 154 =
  40. 40.278 + 664 =

Answer key

  1. 789
  2. 443
  3. 1292
  4. 1038
  5. 263
  6. 393
  7. 572
  8. 299
  9. 1084
  10. 929
  11. 372
  12. 449
  13. 1288
  14. 929
  15. 274
  16. 1147
  17. 211
  18. 1166
  19. 189
  20. 623
  21. 297
  22. 540
  23. 941
  24. 101
  25. 322
  26. 875
  27. 167
  28. 1045
  29. 712
  30. 776
  31. 977
  32. 954
  33. 305
  34. 564
  35. 714
  36. 631
  37. 920
  38. 538
  39. 530
  40. 942

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