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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 359 · 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. 1.147 + 271 =
  2. 2.496 + 357 =
  3. 3.541 + 461 =
  4. 4.810 − 643 =
  5. 5.506 − 206 =
  6. 6.179 + 124 =
  7. 7.823 − 529 =
  8. 8.490 − 298 =
  9. 9.471 − 343 =
  10. 10.583 − 123 =
  11. 11.753 + 349 =
  12. 12.142 + 212 =
  13. 13.245 + 178 =
  14. 14.426 + 115 =
  15. 15.175 + 262 =
  16. 16.840 − 581 =
  17. 17.382 + 515 =
  18. 18.650 − 381 =
  19. 19.452 − 331 =
  20. 20.435 − 301 =
  21. 21.853 − 214 =
  22. 22.416 − 261 =
  23. 23.911 − 566 =
  24. 24.581 − 273 =
  25. 25.920 − 572 =
  26. 26.686 − 514 =
  27. 27.864 − 196 =
  28. 28.713 − 172 =
  29. 29.700 − 544 =
  30. 30.823 − 644 =
  31. 31.268 + 232 =
  32. 32.412 − 288 =
  33. 33.241 + 472 =
  34. 34.870 − 671 =
  35. 35.622 − 321 =
  36. 36.463 + 271 =
  37. 37.475 + 603 =
  38. 38.769 − 304 =
  39. 39.867 − 289 =
  40. 40.507 + 188 =

Answer key

  1. 418
  2. 853
  3. 1002
  4. 167
  5. 300
  6. 303
  7. 294
  8. 192
  9. 128
  10. 460
  11. 1102
  12. 354
  13. 423
  14. 541
  15. 437
  16. 259
  17. 897
  18. 269
  19. 121
  20. 134
  21. 639
  22. 155
  23. 345
  24. 308
  25. 348
  26. 172
  27. 668
  28. 541
  29. 156
  30. 179
  31. 500
  32. 124
  33. 713
  34. 199
  35. 301
  36. 734
  37. 1078
  38. 465
  39. 578
  40. 695

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