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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 583 · 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. 1.139 + 261 =
  2. 2.484 + 669 =
  3. 3.531 − 147 =
  4. 4.938 − 414 =
  5. 5.784 − 233 =
  6. 6.342 + 501 =
  7. 7.473 − 141 =
  8. 8.253 + 239 =
  9. 9.565 + 145 =
  10. 10.538 − 376 =
  11. 11.413 + 415 =
  12. 12.368 + 427 =
  13. 13.988 − 322 =
  14. 14.458 − 269 =
  15. 15.308 + 299 =
  16. 16.321 + 221 =
  17. 17.485 + 656 =
  18. 18.673 − 134 =
  19. 19.525 − 346 =
  20. 20.658 + 131 =
  21. 21.698 + 131 =
  22. 22.560 − 224 =
  23. 23.817 − 424 =
  24. 24.386 + 233 =
  25. 25.242 + 343 =
  26. 26.417 + 142 =
  27. 27.756 − 504 =
  28. 28.782 − 474 =
  29. 29.532 + 128 =
  30. 30.734 − 304 =
  31. 31.552 + 151 =
  32. 32.691 − 213 =
  33. 33.236 + 605 =
  34. 34.621 + 513 =
  35. 35.329 + 175 =
  36. 36.747 − 251 =
  37. 37.615 + 171 =
  38. 38.965 − 451 =
  39. 39.971 − 704 =
  40. 40.142 + 128 =

Answer key

  1. 400
  2. 1153
  3. 384
  4. 524
  5. 551
  6. 843
  7. 332
  8. 492
  9. 710
  10. 162
  11. 828
  12. 795
  13. 666
  14. 189
  15. 607
  16. 542
  17. 1141
  18. 539
  19. 179
  20. 789
  21. 829
  22. 336
  23. 393
  24. 619
  25. 585
  26. 559
  27. 252
  28. 308
  29. 660
  30. 430
  31. 703
  32. 478
  33. 841
  34. 1134
  35. 504
  36. 496
  37. 786
  38. 514
  39. 267
  40. 270

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