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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 259 · 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. 1.469 + 321 =
  2. 2.573 − 226 =
  3. 3.818 − 619 =
  4. 4.303 + 551 =
  5. 5.424 − 121 =
  6. 6.718 − 262 =
  7. 7.318 + 194 =
  8. 8.561 + 509 =
  9. 9.438 − 244 =
  10. 10.537 − 145 =
  11. 11.582 + 271 =
  12. 12.221 + 207 =
  13. 13.480 − 152 =
  14. 14.177 + 508 =
  15. 15.135 + 179 =
  16. 16.856 − 158 =
  17. 17.772 + 177 =
  18. 18.951 − 711 =
  19. 19.196 + 597 =
  20. 20.136 + 321 =
  21. 21.653 + 602 =
  22. 22.801 − 673 =
  23. 23.514 + 226 =
  24. 24.736 + 678 =
  25. 25.913 − 546 =
  26. 26.702 − 169 =
  27. 27.758 + 458 =
  28. 28.455 − 293 =
  29. 29.785 − 624 =
  30. 30.645 + 146 =
  31. 31.704 + 674 =
  32. 32.556 − 273 =
  33. 33.397 + 246 =
  34. 34.330 + 502 =
  35. 35.571 − 318 =
  36. 36.577 − 359 =
  37. 37.430 − 215 =
  38. 38.896 − 601 =
  39. 39.737 − 236 =
  40. 40.634 − 492 =

Answer key

  1. 790
  2. 347
  3. 199
  4. 854
  5. 303
  6. 456
  7. 512
  8. 1070
  9. 194
  10. 392
  11. 853
  12. 428
  13. 328
  14. 685
  15. 314
  16. 698
  17. 949
  18. 240
  19. 793
  20. 457
  21. 1255
  22. 128
  23. 740
  24. 1414
  25. 367
  26. 533
  27. 1216
  28. 162
  29. 161
  30. 791
  31. 1378
  32. 283
  33. 643
  34. 832
  35. 253
  36. 218
  37. 215
  38. 295
  39. 501
  40. 142

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