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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 35 · 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. 1.537 + 481 =
  2. 2.782 − 121 =
  3. 3.785 + 644 =
  4. 4.546 − 416 =
  5. 5.169 + 311 =
  6. 6.714 + 679 =
  7. 7.204 + 549 =
  8. 8.737 + 118 =
  9. 9.809 − 202 =
  10. 10.645 + 233 =
  11. 11.477 + 673 =
  12. 12.834 − 407 =
  13. 13.327 + 122 =
  14. 14.577 − 304 =
  15. 15.451 − 223 =
  16. 16.561 + 402 =
  17. 17.963 − 737 =
  18. 18.425 + 366 =
  19. 19.656 + 279 =
  20. 20.156 + 182 =
  21. 21.841 − 194 =
  22. 22.240 + 351 =
  23. 23.747 + 487 =
  24. 24.701 + 175 =
  25. 25.639 − 387 =
  26. 26.473 − 256 =
  27. 27.421 − 201 =
  28. 28.568 + 667 =
  29. 29.610 + 199 =
  30. 30.437 − 245 =
  31. 31.918 − 337 =
  32. 32.233 + 292 =
  33. 33.564 + 174 =
  34. 34.370 + 201 =
  35. 35.765 + 122 =
  36. 36.873 − 446 =
  37. 37.560 + 152 =
  38. 38.854 − 448 =
  39. 39.499 + 141 =
  40. 40.493 − 207 =

Answer key

  1. 1018
  2. 661
  3. 1429
  4. 130
  5. 480
  6. 1393
  7. 753
  8. 855
  9. 607
  10. 878
  11. 1150
  12. 427
  13. 449
  14. 273
  15. 228
  16. 963
  17. 226
  18. 791
  19. 935
  20. 338
  21. 647
  22. 591
  23. 1234
  24. 876
  25. 252
  26. 217
  27. 220
  28. 1235
  29. 809
  30. 192
  31. 581
  32. 525
  33. 738
  34. 571
  35. 887
  36. 427
  37. 712
  38. 406
  39. 640
  40. 286

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