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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 165 · 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. 1.462 + 382 =
  2. 2.367 + 341 =
  3. 3.354 + 228 =
  4. 4.565 − 148 =
  5. 5.282 + 337 =
  6. 6.551 + 258 =
  7. 7.585 − 253 =
  8. 8.285 + 562 =
  9. 9.533 − 231 =
  10. 10.497 + 493 =
  11. 11.598 − 289 =
  12. 12.687 − 213 =
  13. 13.549 − 253 =
  14. 14.582 − 403 =
  15. 15.191 + 655 =
  16. 16.615 − 391 =
  17. 17.473 + 592 =
  18. 18.526 + 521 =
  19. 19.389 + 556 =
  20. 20.146 + 599 =
  21. 21.385 + 561 =
  22. 22.393 + 271 =
  23. 23.837 − 594 =
  24. 24.386 + 458 =
  25. 25.529 − 193 =
  26. 26.282 + 112 =
  27. 27.654 + 663 =
  28. 28.315 + 281 =
  29. 29.882 − 451 =
  30. 30.942 − 397 =
  31. 31.230 + 593 =
  32. 32.300 + 632 =
  33. 33.425 + 451 =
  34. 34.308 + 301 =
  35. 35.446 − 187 =
  36. 36.821 − 128 =
  37. 37.808 − 592 =
  38. 38.812 − 513 =
  39. 39.301 + 531 =
  40. 40.257 + 614 =

Answer key

  1. 844
  2. 708
  3. 582
  4. 417
  5. 619
  6. 809
  7. 332
  8. 847
  9. 302
  10. 990
  11. 309
  12. 474
  13. 296
  14. 179
  15. 846
  16. 224
  17. 1065
  18. 1047
  19. 945
  20. 745
  21. 946
  22. 664
  23. 243
  24. 844
  25. 336
  26. 394
  27. 1317
  28. 596
  29. 431
  30. 545
  31. 823
  32. 932
  33. 876
  34. 609
  35. 259
  36. 693
  37. 216
  38. 299
  39. 832
  40. 871

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