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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 956 · 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. 1.621 − 231 =
  2. 2.431 + 684 =
  3. 3.588 + 418 =
  4. 4.139 + 319 =
  5. 5.783 + 283 =
  6. 6.793 − 532 =
  7. 7.319 + 398 =
  8. 8.449 + 602 =
  9. 9.212 + 641 =
  10. 10.268 + 513 =
  11. 11.569 + 133 =
  12. 12.631 − 437 =
  13. 13.705 + 355 =
  14. 14.514 − 297 =
  15. 15.375 + 273 =
  16. 16.722 − 146 =
  17. 17.884 − 607 =
  18. 18.559 − 203 =
  19. 19.323 + 352 =
  20. 20.280 + 412 =
  21. 21.801 − 157 =
  22. 22.445 − 118 =
  23. 23.408 + 375 =
  24. 24.460 + 149 =
  25. 25.181 + 481 =
  26. 26.961 − 839 =
  27. 27.763 + 392 =
  28. 28.451 − 249 =
  29. 29.174 + 359 =
  30. 30.501 + 217 =
  31. 31.623 + 176 =
  32. 32.265 + 442 =
  33. 33.338 + 514 =
  34. 34.717 + 285 =
  35. 35.577 − 249 =
  36. 36.161 + 167 =
  37. 37.960 − 803 =
  38. 38.743 − 556 =
  39. 39.467 − 185 =
  40. 40.433 − 155 =

Answer key

  1. 390
  2. 1115
  3. 1006
  4. 458
  5. 1066
  6. 261
  7. 717
  8. 1051
  9. 853
  10. 781
  11. 702
  12. 194
  13. 1060
  14. 217
  15. 648
  16. 576
  17. 277
  18. 356
  19. 675
  20. 692
  21. 644
  22. 327
  23. 783
  24. 609
  25. 662
  26. 122
  27. 1155
  28. 202
  29. 533
  30. 718
  31. 799
  32. 707
  33. 852
  34. 1002
  35. 328
  36. 328
  37. 157
  38. 187
  39. 282
  40. 278

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