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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 2 · 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. 1.642 + 171 =
  2. 2.403 + 208 =
  3. 3.399 + 319 =
  4. 4.541 + 439 =
  5. 5.279 + 536 =
  6. 6.900 − 136 =
  7. 7.814 − 285 =
  8. 8.437 − 135 =
  9. 9.738 + 225 =
  10. 10.665 − 291 =
  11. 11.846 − 718 =
  12. 12.455 + 189 =
  13. 13.406 + 301 =
  14. 14.808 − 178 =
  15. 15.744 − 307 =
  16. 16.718 + 244 =
  17. 17.655 − 192 =
  18. 18.731 − 345 =
  19. 19.735 + 165 =
  20. 20.379 + 323 =
  21. 21.733 − 474 =
  22. 22.595 + 474 =
  23. 23.471 − 134 =
  24. 24.489 + 505 =
  25. 25.176 + 485 =
  26. 26.553 − 321 =
  27. 27.962 − 849 =
  28. 28.762 + 472 =
  29. 29.625 − 222 =
  30. 30.945 − 581 =
  31. 31.913 − 196 =
  32. 32.233 + 417 =
  33. 33.596 + 317 =
  34. 34.570 + 255 =
  35. 35.303 + 371 =
  36. 36.417 − 245 =
  37. 37.279 + 245 =
  38. 38.198 + 372 =
  39. 39.135 + 483 =
  40. 40.741 + 227 =

Answer key

  1. 813
  2. 611
  3. 718
  4. 980
  5. 815
  6. 764
  7. 529
  8. 302
  9. 963
  10. 374
  11. 128
  12. 644
  13. 707
  14. 630
  15. 437
  16. 962
  17. 463
  18. 386
  19. 900
  20. 702
  21. 259
  22. 1069
  23. 337
  24. 994
  25. 661
  26. 232
  27. 113
  28. 1234
  29. 403
  30. 364
  31. 717
  32. 650
  33. 913
  34. 825
  35. 674
  36. 172
  37. 524
  38. 570
  39. 618
  40. 968

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