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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 87 · 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. 1.428 + 347 =
  2. 2.273 + 407 =
  3. 3.786 + 161 =
  4. 4.619 − 441 =
  5. 5.667 − 129 =
  6. 6.823 − 339 =
  7. 7.518 − 375 =
  8. 8.647 + 285 =
  9. 9.145 + 378 =
  10. 10.568 + 518 =
  11. 11.531 − 319 =
  12. 12.816 − 139 =
  13. 13.545 + 155 =
  14. 14.531 + 365 =
  15. 15.280 + 233 =
  16. 16.164 + 565 =
  17. 17.493 − 191 =
  18. 18.174 + 551 =
  19. 19.359 + 491 =
  20. 20.680 − 453 =
  21. 21.209 + 241 =
  22. 22.784 + 172 =
  23. 23.428 − 223 =
  24. 24.311 + 354 =
  25. 25.879 − 363 =
  26. 26.710 − 457 =
  27. 27.325 + 423 =
  28. 28.750 − 503 =
  29. 29.496 − 203 =
  30. 30.199 + 641 =
  31. 31.771 + 174 =
  32. 32.777 + 631 =
  33. 33.181 + 571 =
  34. 34.657 + 605 =
  35. 35.393 + 542 =
  36. 36.700 + 431 =
  37. 37.188 + 118 =
  38. 38.144 + 657 =
  39. 39.596 − 414 =
  40. 40.576 − 265 =

Answer key

  1. 775
  2. 680
  3. 947
  4. 178
  5. 538
  6. 484
  7. 143
  8. 932
  9. 523
  10. 1086
  11. 212
  12. 677
  13. 700
  14. 896
  15. 513
  16. 729
  17. 302
  18. 725
  19. 850
  20. 227
  21. 450
  22. 956
  23. 205
  24. 665
  25. 516
  26. 253
  27. 748
  28. 247
  29. 293
  30. 840
  31. 945
  32. 1408
  33. 752
  34. 1262
  35. 935
  36. 1131
  37. 306
  38. 801
  39. 182
  40. 311

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