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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 356 · 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. 1.448 + 309 =
  2. 2.973 − 847 =
  3. 3.781 − 566 =
  4. 4.958 − 208 =
  5. 5.617 + 232 =
  6. 6.178 + 371 =
  7. 7.626 − 519 =
  8. 8.559 − 189 =
  9. 9.570 − 235 =
  10. 10.654 − 362 =
  11. 11.709 + 206 =
  12. 12.438 − 236 =
  13. 13.759 − 249 =
  14. 14.457 − 314 =
  15. 15.592 + 364 =
  16. 16.698 − 498 =
  17. 17.480 − 265 =
  18. 18.606 + 635 =
  19. 19.644 − 203 =
  20. 20.721 + 175 =
  21. 21.628 + 678 =
  22. 22.461 − 343 =
  23. 23.988 − 293 =
  24. 24.607 − 481 =
  25. 25.532 + 452 =
  26. 26.523 − 411 =
  27. 27.579 + 451 =
  28. 28.202 + 511 =
  29. 29.295 + 485 =
  30. 30.887 − 233 =
  31. 31.433 − 175 =
  32. 32.807 − 641 =
  33. 33.589 + 185 =
  34. 34.601 + 322 =
  35. 35.562 + 678 =
  36. 36.754 + 195 =
  37. 37.642 − 439 =
  38. 38.314 + 517 =
  39. 39.830 − 289 =
  40. 40.229 + 221 =

Answer key

  1. 757
  2. 126
  3. 215
  4. 750
  5. 849
  6. 549
  7. 107
  8. 370
  9. 335
  10. 292
  11. 915
  12. 202
  13. 510
  14. 143
  15. 956
  16. 200
  17. 215
  18. 1241
  19. 441
  20. 896
  21. 1306
  22. 118
  23. 695
  24. 126
  25. 984
  26. 112
  27. 1030
  28. 713
  29. 780
  30. 654
  31. 258
  32. 166
  33. 774
  34. 923
  35. 1240
  36. 949
  37. 203
  38. 831
  39. 541
  40. 450

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