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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 27 · 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. 1.755 + 296 =
  2. 2.473 − 136 =
  3. 3.681 + 578 =
  4. 4.979 − 446 =
  5. 5.471 − 161 =
  6. 6.283 + 403 =
  7. 7.235 + 565 =
  8. 8.426 + 532 =
  9. 9.605 + 431 =
  10. 10.726 + 538 =
  11. 11.428 + 579 =
  12. 12.839 − 662 =
  13. 13.615 − 392 =
  14. 14.412 − 306 =
  15. 15.905 − 462 =
  16. 16.626 + 255 =
  17. 17.503 + 291 =
  18. 18.621 − 254 =
  19. 19.709 − 289 =
  20. 20.779 + 362 =
  21. 21.919 − 309 =
  22. 22.473 − 121 =
  23. 23.141 + 187 =
  24. 24.563 + 158 =
  25. 25.827 − 273 =
  26. 26.646 + 305 =
  27. 27.929 − 558 =
  28. 28.479 − 202 =
  29. 29.321 + 681 =
  30. 30.727 + 276 =
  31. 31.410 + 596 =
  32. 32.487 − 182 =
  33. 33.484 + 274 =
  34. 34.163 + 622 =
  35. 35.310 + 506 =
  36. 36.324 + 224 =
  37. 37.948 − 688 =
  38. 38.717 − 554 =
  39. 39.608 + 486 =
  40. 40.265 + 579 =

Answer key

  1. 1051
  2. 337
  3. 1259
  4. 533
  5. 310
  6. 686
  7. 800
  8. 958
  9. 1036
  10. 1264
  11. 1007
  12. 177
  13. 223
  14. 106
  15. 443
  16. 881
  17. 794
  18. 367
  19. 420
  20. 1141
  21. 610
  22. 352
  23. 328
  24. 721
  25. 554
  26. 951
  27. 371
  28. 277
  29. 1002
  30. 1003
  31. 1006
  32. 305
  33. 758
  34. 785
  35. 816
  36. 548
  37. 260
  38. 163
  39. 1094
  40. 844

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