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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 352 · 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. 1.718 − 594 =
  2. 2.799 − 374 =
  3. 3.707 + 541 =
  4. 4.631 − 394 =
  5. 5.703 − 421 =
  6. 6.351 + 275 =
  7. 7.294 + 631 =
  8. 8.483 − 347 =
  9. 9.972 − 287 =
  10. 10.712 − 571 =
  11. 11.437 − 171 =
  12. 12.761 + 121 =
  13. 13.130 + 508 =
  14. 14.156 + 407 =
  15. 15.225 + 394 =
  16. 16.600 − 442 =
  17. 17.496 + 603 =
  18. 18.906 − 398 =
  19. 19.490 − 165 =
  20. 20.492 + 506 =
  21. 21.264 + 286 =
  22. 22.754 + 532 =
  23. 23.197 + 245 =
  24. 24.477 + 467 =
  25. 25.693 − 283 =
  26. 26.601 + 442 =
  27. 27.503 − 398 =
  28. 28.702 − 293 =
  29. 29.430 + 353 =
  30. 30.896 − 443 =
  31. 31.430 − 268 =
  32. 32.714 + 564 =
  33. 33.384 + 298 =
  34. 34.681 + 146 =
  35. 35.973 − 493 =
  36. 36.625 − 175 =
  37. 37.687 − 298 =
  38. 38.139 + 391 =
  39. 39.937 − 579 =
  40. 40.741 + 535 =

Answer key

  1. 124
  2. 425
  3. 1248
  4. 237
  5. 282
  6. 626
  7. 925
  8. 136
  9. 685
  10. 141
  11. 266
  12. 882
  13. 638
  14. 563
  15. 619
  16. 158
  17. 1099
  18. 508
  19. 325
  20. 998
  21. 550
  22. 1286
  23. 442
  24. 944
  25. 410
  26. 1043
  27. 105
  28. 409
  29. 783
  30. 453
  31. 162
  32. 1278
  33. 682
  34. 827
  35. 480
  36. 450
  37. 389
  38. 530
  39. 358
  40. 1276

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