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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 114 · 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. 1.637 − 455 =
  2. 2.536 − 241 =
  3. 3.723 − 576 =
  4. 4.131 + 211 =
  5. 5.566 + 262 =
  6. 6.162 + 292 =
  7. 7.534 + 248 =
  8. 8.799 − 145 =
  9. 9.736 − 403 =
  10. 10.283 + 611 =
  11. 11.417 − 308 =
  12. 12.213 + 279 =
  13. 13.244 + 543 =
  14. 14.217 + 458 =
  15. 15.455 − 266 =
  16. 16.818 − 251 =
  17. 17.433 − 146 =
  18. 18.258 + 481 =
  19. 19.877 − 589 =
  20. 20.852 − 516 =
  21. 21.499 + 197 =
  22. 22.551 − 338 =
  23. 23.625 − 366 =
  24. 24.978 − 625 =
  25. 25.777 + 636 =
  26. 26.515 + 553 =
  27. 27.785 − 366 =
  28. 28.604 + 127 =
  29. 29.145 + 474 =
  30. 30.877 − 208 =
  31. 31.283 + 532 =
  32. 32.858 − 205 =
  33. 33.188 + 223 =
  34. 34.227 + 165 =
  35. 35.234 + 299 =
  36. 36.134 + 135 =
  37. 37.254 + 244 =
  38. 38.685 + 617 =
  39. 39.189 + 265 =
  40. 40.340 + 671 =

Answer key

  1. 182
  2. 295
  3. 147
  4. 342
  5. 828
  6. 454
  7. 782
  8. 654
  9. 333
  10. 894
  11. 109
  12. 492
  13. 787
  14. 675
  15. 189
  16. 567
  17. 287
  18. 739
  19. 288
  20. 336
  21. 696
  22. 213
  23. 259
  24. 353
  25. 1413
  26. 1068
  27. 419
  28. 731
  29. 619
  30. 669
  31. 815
  32. 653
  33. 411
  34. 392
  35. 533
  36. 269
  37. 498
  38. 1302
  39. 454
  40. 1011

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