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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 325 · 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. 1.276 + 154 =
  2. 2.554 − 409 =
  3. 3.500 − 335 =
  4. 4.191 + 391 =
  5. 5.533 + 261 =
  6. 6.523 − 352 =
  7. 7.180 + 668 =
  8. 8.900 − 147 =
  9. 9.137 + 247 =
  10. 10.350 + 539 =
  11. 11.574 − 346 =
  12. 12.874 − 507 =
  13. 13.400 + 146 =
  14. 14.308 + 113 =
  15. 15.650 − 131 =
  16. 16.648 − 503 =
  17. 17.212 + 389 =
  18. 18.756 + 464 =
  19. 19.193 + 352 =
  20. 20.149 + 633 =
  21. 21.290 + 144 =
  22. 22.940 − 431 =
  23. 23.648 + 641 =
  24. 24.463 − 326 =
  25. 25.502 − 286 =
  26. 26.822 − 445 =
  27. 27.566 − 401 =
  28. 28.435 + 125 =
  29. 29.693 + 176 =
  30. 30.600 + 665 =
  31. 31.672 − 464 =
  32. 32.699 − 139 =
  33. 33.481 − 265 =
  34. 34.355 + 326 =
  35. 35.922 − 304 =
  36. 36.270 + 476 =
  37. 37.768 − 523 =
  38. 38.445 − 236 =
  39. 39.464 + 207 =
  40. 40.452 − 239 =

Answer key

  1. 430
  2. 145
  3. 165
  4. 582
  5. 794
  6. 171
  7. 848
  8. 753
  9. 384
  10. 889
  11. 228
  12. 367
  13. 546
  14. 421
  15. 519
  16. 145
  17. 601
  18. 1220
  19. 545
  20. 782
  21. 434
  22. 509
  23. 1289
  24. 137
  25. 216
  26. 377
  27. 165
  28. 560
  29. 869
  30. 1265
  31. 208
  32. 560
  33. 216
  34. 681
  35. 618
  36. 746
  37. 245
  38. 209
  39. 671
  40. 213

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