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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 395 · 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. 1.666 + 599 =
  2. 2.692 − 383 =
  3. 3.577 − 135 =
  4. 4.692 + 511 =
  5. 5.434 + 513 =
  6. 6.441 + 161 =
  7. 7.209 + 433 =
  8. 8.928 − 772 =
  9. 9.525 − 403 =
  10. 10.679 − 245 =
  11. 11.468 + 254 =
  12. 12.244 + 413 =
  13. 13.569 + 354 =
  14. 14.748 − 615 =
  15. 15.164 + 121 =
  16. 16.309 + 243 =
  17. 17.764 + 606 =
  18. 18.879 − 644 =
  19. 19.738 − 347 =
  20. 20.126 + 251 =
  21. 21.749 + 198 =
  22. 22.286 + 616 =
  23. 23.554 + 429 =
  24. 24.780 + 326 =
  25. 25.710 + 301 =
  26. 26.639 − 113 =
  27. 27.695 + 455 =
  28. 28.236 + 408 =
  29. 29.539 − 386 =
  30. 30.796 − 447 =
  31. 31.875 − 355 =
  32. 32.486 − 296 =
  33. 33.330 + 518 =
  34. 34.566 − 216 =
  35. 35.840 − 688 =
  36. 36.790 − 285 =
  37. 37.498 + 647 =
  38. 38.492 + 673 =
  39. 39.267 + 177 =
  40. 40.197 + 124 =

Answer key

  1. 1265
  2. 309
  3. 442
  4. 1203
  5. 947
  6. 602
  7. 642
  8. 156
  9. 122
  10. 434
  11. 722
  12. 657
  13. 923
  14. 133
  15. 285
  16. 552
  17. 1370
  18. 235
  19. 391
  20. 377
  21. 947
  22. 902
  23. 983
  24. 1106
  25. 1011
  26. 526
  27. 1150
  28. 644
  29. 153
  30. 349
  31. 520
  32. 190
  33. 848
  34. 350
  35. 152
  36. 505
  37. 1145
  38. 1165
  39. 444
  40. 321

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