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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 523 · 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. 1.144 + 166 =
  2. 2.482 + 202 =
  3. 3.559 + 391 =
  4. 4.432 + 159 =
  5. 5.207 + 403 =
  6. 6.887 − 121 =
  7. 7.445 + 646 =
  8. 8.548 − 131 =
  9. 9.780 + 161 =
  10. 10.732 − 269 =
  11. 11.782 + 504 =
  12. 12.422 + 589 =
  13. 13.600 − 192 =
  14. 14.898 − 171 =
  15. 15.641 + 474 =
  16. 16.462 − 237 =
  17. 17.337 + 624 =
  18. 18.856 − 143 =
  19. 19.451 − 328 =
  20. 20.663 + 202 =
  21. 21.987 − 275 =
  22. 22.248 + 437 =
  23. 23.701 + 142 =
  24. 24.436 − 321 =
  25. 25.710 + 203 =
  26. 26.604 + 334 =
  27. 27.938 − 525 =
  28. 28.622 + 508 =
  29. 29.209 + 309 =
  30. 30.634 + 134 =
  31. 31.736 + 402 =
  32. 32.628 − 486 =
  33. 33.894 − 726 =
  34. 34.587 − 181 =
  35. 35.819 − 365 =
  36. 36.487 + 496 =
  37. 37.464 − 256 =
  38. 38.527 − 253 =
  39. 39.424 + 421 =
  40. 40.886 − 216 =

Answer key

  1. 310
  2. 684
  3. 950
  4. 591
  5. 610
  6. 766
  7. 1091
  8. 417
  9. 941
  10. 463
  11. 1286
  12. 1011
  13. 408
  14. 727
  15. 1115
  16. 225
  17. 961
  18. 713
  19. 123
  20. 865
  21. 712
  22. 685
  23. 843
  24. 115
  25. 913
  26. 938
  27. 413
  28. 1130
  29. 518
  30. 768
  31. 1138
  32. 142
  33. 168
  34. 406
  35. 454
  36. 983
  37. 208
  38. 274
  39. 845
  40. 670

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