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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 829 · 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. 1.674 − 254 =
  2. 2.296 + 203 =
  3. 3.629 − 133 =
  4. 4.778 + 151 =
  5. 5.274 + 221 =
  6. 6.664 − 394 =
  7. 7.347 + 131 =
  8. 8.550 + 665 =
  9. 9.448 − 247 =
  10. 10.127 + 432 =
  11. 11.451 − 178 =
  12. 12.557 + 256 =
  13. 13.467 + 542 =
  14. 14.144 + 194 =
  15. 15.212 + 323 =
  16. 16.440 − 191 =
  17. 17.672 − 192 =
  18. 18.195 + 558 =
  19. 19.423 + 553 =
  20. 20.647 − 404 =
  21. 21.681 + 162 =
  22. 22.936 − 727 =
  23. 23.541 + 351 =
  24. 24.758 + 563 =
  25. 25.506 − 279 =
  26. 26.693 + 123 =
  27. 27.427 − 221 =
  28. 28.620 + 181 =
  29. 29.539 − 398 =
  30. 30.704 − 514 =
  31. 31.482 + 179 =
  32. 32.459 − 328 =
  33. 33.194 + 273 =
  34. 34.702 + 381 =
  35. 35.497 + 363 =
  36. 36.477 − 339 =
  37. 37.132 + 316 =
  38. 38.567 + 305 =
  39. 39.545 − 409 =
  40. 40.723 − 364 =

Answer key

  1. 420
  2. 499
  3. 496
  4. 929
  5. 495
  6. 270
  7. 478
  8. 1215
  9. 201
  10. 559
  11. 273
  12. 813
  13. 1009
  14. 338
  15. 535
  16. 249
  17. 480
  18. 753
  19. 976
  20. 243
  21. 843
  22. 209
  23. 892
  24. 1321
  25. 227
  26. 816
  27. 206
  28. 801
  29. 141
  30. 190
  31. 661
  32. 131
  33. 467
  34. 1083
  35. 860
  36. 138
  37. 448
  38. 872
  39. 136
  40. 359

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