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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 820 · 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. 1.507 + 457 =
  2. 2.629 + 646 =
  3. 3.575 − 349 =
  4. 4.288 + 367 =
  5. 5.292 + 439 =
  6. 6.189 + 461 =
  7. 7.506 − 183 =
  8. 8.610 + 661 =
  9. 9.750 − 483 =
  10. 10.834 − 531 =
  11. 11.518 − 117 =
  12. 12.979 − 587 =
  13. 13.133 + 151 =
  14. 14.843 − 241 =
  15. 15.446 + 609 =
  16. 16.184 + 191 =
  17. 17.914 − 364 =
  18. 18.873 − 447 =
  19. 19.681 − 314 =
  20. 20.954 − 294 =
  21. 21.233 + 311 =
  22. 22.695 + 631 =
  23. 23.489 − 301 =
  24. 24.549 + 334 =
  25. 25.168 + 214 =
  26. 26.718 + 279 =
  27. 27.577 − 379 =
  28. 28.137 + 661 =
  29. 29.416 + 399 =
  30. 30.430 − 208 =
  31. 31.529 + 136 =
  32. 32.564 − 203 =
  33. 33.407 + 395 =
  34. 34.405 + 123 =
  35. 35.857 − 418 =
  36. 36.267 + 353 =
  37. 37.789 + 624 =
  38. 38.886 − 216 =
  39. 39.561 + 629 =
  40. 40.833 − 593 =

Answer key

  1. 964
  2. 1275
  3. 226
  4. 655
  5. 731
  6. 650
  7. 323
  8. 1271
  9. 267
  10. 303
  11. 401
  12. 392
  13. 284
  14. 602
  15. 1055
  16. 375
  17. 550
  18. 426
  19. 367
  20. 660
  21. 544
  22. 1326
  23. 188
  24. 883
  25. 382
  26. 997
  27. 198
  28. 798
  29. 815
  30. 222
  31. 665
  32. 361
  33. 802
  34. 528
  35. 439
  36. 620
  37. 1413
  38. 670
  39. 1190
  40. 240

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