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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 463 · 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. 1.145 + 392 =
  2. 2.517 + 471 =
  3. 3.422 − 315 =
  4. 4.894 − 694 =
  5. 5.647 − 328 =
  6. 6.620 − 123 =
  7. 7.428 − 121 =
  8. 8.974 − 584 =
  9. 9.948 − 342 =
  10. 10.423 − 125 =
  11. 11.457 − 124 =
  12. 12.138 + 395 =
  13. 13.126 + 288 =
  14. 14.514 + 462 =
  15. 15.765 + 429 =
  16. 16.666 − 115 =
  17. 17.435 − 139 =
  18. 18.435 − 269 =
  19. 19.503 − 399 =
  20. 20.708 + 394 =
  21. 21.780 − 137 =
  22. 22.718 + 119 =
  23. 23.810 − 335 =
  24. 24.397 + 645 =
  25. 25.378 + 157 =
  26. 26.500 + 396 =
  27. 27.393 + 461 =
  28. 28.629 + 212 =
  29. 29.331 + 601 =
  30. 30.457 + 438 =
  31. 31.585 − 307 =
  32. 32.620 − 347 =
  33. 33.653 − 192 =
  34. 34.594 + 494 =
  35. 35.556 + 301 =
  36. 36.708 − 194 =
  37. 37.693 − 518 =
  38. 38.796 − 401 =
  39. 39.550 + 165 =
  40. 40.607 − 438 =

Answer key

  1. 537
  2. 988
  3. 107
  4. 200
  5. 319
  6. 497
  7. 307
  8. 390
  9. 606
  10. 298
  11. 333
  12. 533
  13. 414
  14. 976
  15. 1194
  16. 551
  17. 296
  18. 166
  19. 104
  20. 1102
  21. 643
  22. 837
  23. 475
  24. 1042
  25. 535
  26. 896
  27. 854
  28. 841
  29. 932
  30. 895
  31. 278
  32. 273
  33. 461
  34. 1088
  35. 857
  36. 514
  37. 175
  38. 395
  39. 715
  40. 169

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