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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 687 · 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. 1.431 + 256 =
  2. 2.382 + 508 =
  3. 3.981 − 245 =
  4. 4.147 + 228 =
  5. 5.622 + 207 =
  6. 6.717 + 613 =
  7. 7.700 + 231 =
  8. 8.462 − 147 =
  9. 9.261 + 271 =
  10. 10.246 + 351 =
  11. 11.854 − 744 =
  12. 12.779 + 207 =
  13. 13.767 − 497 =
  14. 14.744 + 211 =
  15. 15.204 + 278 =
  16. 16.630 + 625 =
  17. 17.472 − 329 =
  18. 18.555 + 323 =
  19. 19.486 − 162 =
  20. 20.571 + 135 =
  21. 21.318 + 393 =
  22. 22.592 + 561 =
  23. 23.767 − 125 =
  24. 24.726 + 463 =
  25. 25.744 − 314 =
  26. 26.565 − 369 =
  27. 27.476 − 201 =
  28. 28.529 + 675 =
  29. 29.545 − 442 =
  30. 30.594 + 135 =
  31. 31.913 − 402 =
  32. 32.555 − 394 =
  33. 33.675 + 174 =
  34. 34.597 − 415 =
  35. 35.398 + 612 =
  36. 36.686 − 291 =
  37. 37.569 + 379 =
  38. 38.592 + 134 =
  39. 39.533 − 141 =
  40. 40.441 − 232 =

Answer key

  1. 687
  2. 890
  3. 736
  4. 375
  5. 829
  6. 1330
  7. 931
  8. 315
  9. 532
  10. 597
  11. 110
  12. 986
  13. 270
  14. 955
  15. 482
  16. 1255
  17. 143
  18. 878
  19. 324
  20. 706
  21. 711
  22. 1153
  23. 642
  24. 1189
  25. 430
  26. 196
  27. 275
  28. 1204
  29. 103
  30. 729
  31. 511
  32. 161
  33. 849
  34. 182
  35. 1010
  36. 395
  37. 948
  38. 726
  39. 392
  40. 209

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