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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 387 · 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. 1.179 + 194 =
  2. 2.705 + 261 =
  3. 3.705 + 583 =
  4. 4.153 + 666 =
  5. 5.782 + 571 =
  6. 6.500 + 594 =
  7. 7.294 + 179 =
  8. 8.751 + 455 =
  9. 9.686 + 229 =
  10. 10.386 + 181 =
  11. 11.822 − 234 =
  12. 12.759 − 256 =
  13. 13.452 + 247 =
  14. 14.753 − 518 =
  15. 15.359 + 316 =
  16. 16.428 − 201 =
  17. 17.406 + 332 =
  18. 18.343 + 204 =
  19. 19.489 − 143 =
  20. 20.648 + 681 =
  21. 21.457 − 186 =
  22. 22.621 − 408 =
  23. 23.466 + 584 =
  24. 24.253 + 185 =
  25. 25.346 + 369 =
  26. 26.573 + 391 =
  27. 27.434 − 197 =
  28. 28.591 + 272 =
  29. 29.349 + 123 =
  30. 30.203 + 558 =
  31. 31.290 + 174 =
  32. 32.709 + 501 =
  33. 33.484 + 274 =
  34. 34.980 − 377 =
  35. 35.742 + 562 =
  36. 36.787 − 365 =
  37. 37.662 − 367 =
  38. 38.401 + 634 =
  39. 39.742 + 488 =
  40. 40.765 + 513 =

Answer key

  1. 373
  2. 966
  3. 1288
  4. 819
  5. 1353
  6. 1094
  7. 473
  8. 1206
  9. 915
  10. 567
  11. 588
  12. 503
  13. 699
  14. 235
  15. 675
  16. 227
  17. 738
  18. 547
  19. 346
  20. 1329
  21. 271
  22. 213
  23. 1050
  24. 438
  25. 715
  26. 964
  27. 237
  28. 863
  29. 472
  30. 761
  31. 464
  32. 1210
  33. 758
  34. 603
  35. 1304
  36. 422
  37. 295
  38. 1035
  39. 1230
  40. 1278

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