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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 432 · 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. 1.379 + 125 =
  2. 2.744 − 145 =
  3. 3.328 + 522 =
  4. 4.301 + 279 =
  5. 5.236 + 465 =
  6. 6.859 − 291 =
  7. 7.381 + 157 =
  8. 8.617 − 321 =
  9. 9.486 − 226 =
  10. 10.798 − 166 =
  11. 11.355 + 157 =
  12. 12.552 + 262 =
  13. 13.650 − 442 =
  14. 14.721 − 346 =
  15. 15.561 − 271 =
  16. 16.488 − 153 =
  17. 17.571 + 461 =
  18. 18.760 − 148 =
  19. 19.783 + 377 =
  20. 20.666 − 237 =
  21. 21.600 + 686 =
  22. 22.412 + 591 =
  23. 23.570 − 311 =
  24. 24.980 − 352 =
  25. 25.949 − 349 =
  26. 26.944 − 201 =
  27. 27.138 + 568 =
  28. 28.620 − 202 =
  29. 29.806 − 455 =
  30. 30.470 − 167 =
  31. 31.513 + 263 =
  32. 32.733 − 263 =
  33. 33.445 − 331 =
  34. 34.834 − 201 =
  35. 35.651 + 272 =
  36. 36.894 − 771 =
  37. 37.797 − 344 =
  38. 38.431 + 643 =
  39. 39.492 + 247 =
  40. 40.575 − 398 =

Answer key

  1. 504
  2. 599
  3. 850
  4. 580
  5. 701
  6. 568
  7. 538
  8. 296
  9. 260
  10. 632
  11. 512
  12. 814
  13. 208
  14. 375
  15. 290
  16. 335
  17. 1032
  18. 612
  19. 1160
  20. 429
  21. 1286
  22. 1003
  23. 259
  24. 628
  25. 600
  26. 743
  27. 706
  28. 418
  29. 351
  30. 303
  31. 776
  32. 470
  33. 114
  34. 633
  35. 923
  36. 123
  37. 453
  38. 1074
  39. 739
  40. 177

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