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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 285 · 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. 1.821 − 351 =
  2. 2.145 + 474 =
  3. 3.583 + 626 =
  4. 4.865 − 522 =
  5. 5.169 + 506 =
  6. 6.211 + 129 =
  7. 7.940 − 343 =
  8. 8.383 + 401 =
  9. 9.453 − 276 =
  10. 10.552 − 404 =
  11. 11.528 − 313 =
  12. 12.414 − 248 =
  13. 13.658 − 241 =
  14. 14.699 + 685 =
  15. 15.177 + 133 =
  16. 16.315 + 254 =
  17. 17.631 − 184 =
  18. 18.328 + 301 =
  19. 19.796 − 209 =
  20. 20.490 + 279 =
  21. 21.207 + 311 =
  22. 22.774 + 249 =
  23. 23.165 + 509 =
  24. 24.315 + 147 =
  25. 25.576 − 434 =
  26. 26.763 + 245 =
  27. 27.804 − 205 =
  28. 28.782 + 394 =
  29. 29.895 − 644 =
  30. 30.526 − 398 =
  31. 31.857 − 716 =
  32. 32.546 − 147 =
  33. 33.706 + 517 =
  34. 34.526 − 373 =
  35. 35.744 − 639 =
  36. 36.573 − 198 =
  37. 37.272 + 119 =
  38. 38.845 − 664 =
  39. 39.598 − 215 =
  40. 40.829 − 663 =

Answer key

  1. 470
  2. 619
  3. 1209
  4. 343
  5. 675
  6. 340
  7. 597
  8. 784
  9. 177
  10. 148
  11. 215
  12. 166
  13. 417
  14. 1384
  15. 310
  16. 569
  17. 447
  18. 629
  19. 587
  20. 769
  21. 518
  22. 1023
  23. 674
  24. 462
  25. 142
  26. 1008
  27. 599
  28. 1176
  29. 251
  30. 128
  31. 141
  32. 399
  33. 1223
  34. 153
  35. 105
  36. 375
  37. 391
  38. 181
  39. 383
  40. 166

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