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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 438 · 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. 1.446 − 138 =
  2. 2.934 − 447 =
  3. 3.756 − 127 =
  4. 4.727 + 239 =
  5. 5.525 − 413 =
  6. 6.696 + 253 =
  7. 7.175 + 351 =
  8. 8.336 + 366 =
  9. 9.546 + 444 =
  10. 10.407 + 498 =
  11. 11.371 + 352 =
  12. 12.878 − 247 =
  13. 13.549 − 393 =
  14. 14.792 − 545 =
  15. 15.636 − 125 =
  16. 16.797 − 619 =
  17. 17.756 + 617 =
  18. 18.467 + 428 =
  19. 19.652 + 433 =
  20. 20.578 + 159 =
  21. 21.510 − 256 =
  22. 22.196 + 589 =
  23. 23.547 + 555 =
  24. 24.141 + 625 =
  25. 25.431 + 342 =
  26. 26.124 + 306 =
  27. 27.302 + 319 =
  28. 28.197 + 568 =
  29. 29.797 − 543 =
  30. 30.627 + 483 =
  31. 31.675 − 215 =
  32. 32.862 − 297 =
  33. 33.263 + 546 =
  34. 34.221 + 237 =
  35. 35.476 + 603 =
  36. 36.910 − 522 =
  37. 37.238 + 397 =
  38. 38.424 − 275 =
  39. 39.718 − 481 =
  40. 40.594 + 591 =

Answer key

  1. 308
  2. 487
  3. 629
  4. 966
  5. 112
  6. 949
  7. 526
  8. 702
  9. 990
  10. 905
  11. 723
  12. 631
  13. 156
  14. 247
  15. 511
  16. 178
  17. 1373
  18. 895
  19. 1085
  20. 737
  21. 254
  22. 785
  23. 1102
  24. 766
  25. 773
  26. 430
  27. 621
  28. 765
  29. 254
  30. 1110
  31. 460
  32. 565
  33. 809
  34. 458
  35. 1079
  36. 388
  37. 635
  38. 149
  39. 237
  40. 1185

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