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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 24 · 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. 1.376 + 144 =
  2. 2.500 + 413 =
  3. 3.523 + 642 =
  4. 4.675 − 405 =
  5. 5.669 + 444 =
  6. 6.902 − 655 =
  7. 7.586 + 534 =
  8. 8.354 + 654 =
  9. 9.356 + 275 =
  10. 10.546 + 591 =
  11. 11.679 + 276 =
  12. 12.590 + 427 =
  13. 13.595 + 328 =
  14. 14.510 + 441 =
  15. 15.358 + 316 =
  16. 16.252 + 596 =
  17. 17.949 − 696 =
  18. 18.702 − 351 =
  19. 19.983 − 666 =
  20. 20.618 + 273 =
  21. 21.223 + 601 =
  22. 22.470 − 277 =
  23. 23.566 + 285 =
  24. 24.565 + 389 =
  25. 25.337 + 372 =
  26. 26.944 − 765 =
  27. 27.550 + 226 =
  28. 28.132 + 487 =
  29. 29.418 − 168 =
  30. 30.533 − 198 =
  31. 31.494 + 327 =
  32. 32.365 + 172 =
  33. 33.688 − 578 =
  34. 34.451 + 381 =
  35. 35.236 + 213 =
  36. 36.151 + 451 =
  37. 37.750 − 536 =
  38. 38.401 + 232 =
  39. 39.646 − 546 =
  40. 40.330 + 508 =

Answer key

  1. 520
  2. 913
  3. 1165
  4. 270
  5. 1113
  6. 247
  7. 1120
  8. 1008
  9. 631
  10. 1137
  11. 955
  12. 1017
  13. 923
  14. 951
  15. 674
  16. 848
  17. 253
  18. 351
  19. 317
  20. 891
  21. 824
  22. 193
  23. 851
  24. 954
  25. 709
  26. 179
  27. 776
  28. 619
  29. 250
  30. 335
  31. 821
  32. 537
  33. 110
  34. 832
  35. 449
  36. 602
  37. 214
  38. 633
  39. 100
  40. 838

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