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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 818 · 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. 1.759 + 599 =
  2. 2.959 − 433 =
  3. 3.316 + 133 =
  4. 4.543 − 417 =
  5. 5.712 + 167 =
  6. 6.766 + 361 =
  7. 7.257 + 137 =
  8. 8.352 + 689 =
  9. 9.416 − 279 =
  10. 10.532 + 544 =
  11. 11.450 + 193 =
  12. 12.328 + 501 =
  13. 13.688 + 556 =
  14. 14.427 + 265 =
  15. 15.646 − 389 =
  16. 16.413 − 133 =
  17. 17.591 − 385 =
  18. 18.690 + 416 =
  19. 19.817 − 205 =
  20. 20.627 − 369 =
  21. 21.782 − 425 =
  22. 22.427 − 271 =
  23. 23.898 − 202 =
  24. 24.343 + 302 =
  25. 25.618 + 656 =
  26. 26.636 + 295 =
  27. 27.886 − 462 =
  28. 28.510 − 298 =
  29. 29.775 − 169 =
  30. 30.933 − 231 =
  31. 31.834 − 211 =
  32. 32.283 + 504 =
  33. 33.250 + 679 =
  34. 34.463 − 177 =
  35. 35.973 − 509 =
  36. 36.231 + 304 =
  37. 37.211 + 681 =
  38. 38.555 + 143 =
  39. 39.679 + 531 =
  40. 40.343 + 241 =

Answer key

  1. 1358
  2. 526
  3. 449
  4. 126
  5. 879
  6. 1127
  7. 394
  8. 1041
  9. 137
  10. 1076
  11. 643
  12. 829
  13. 1244
  14. 692
  15. 257
  16. 280
  17. 206
  18. 1106
  19. 612
  20. 258
  21. 357
  22. 156
  23. 696
  24. 645
  25. 1274
  26. 931
  27. 424
  28. 212
  29. 606
  30. 702
  31. 623
  32. 787
  33. 929
  34. 286
  35. 464
  36. 535
  37. 892
  38. 698
  39. 1210
  40. 584

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