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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 656 · 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. 1.446 + 201 =
  2. 2.542 + 401 =
  3. 3.456 + 515 =
  4. 4.510 − 407 =
  5. 5.613 − 244 =
  6. 6.744 + 125 =
  7. 7.617 + 558 =
  8. 8.984 − 421 =
  9. 9.809 − 544 =
  10. 10.241 + 499 =
  11. 11.851 − 416 =
  12. 12.938 − 815 =
  13. 13.290 + 471 =
  14. 14.518 − 368 =
  15. 15.841 − 711 =
  16. 16.751 + 175 =
  17. 17.153 + 248 =
  18. 18.608 − 502 =
  19. 19.243 + 157 =
  20. 20.658 − 476 =
  21. 21.950 − 394 =
  22. 22.512 + 312 =
  23. 23.935 − 552 =
  24. 24.706 − 161 =
  25. 25.928 − 791 =
  26. 26.486 − 269 =
  27. 27.205 + 688 =
  28. 28.229 + 575 =
  29. 29.181 + 324 =
  30. 30.453 − 278 =
  31. 31.803 − 551 =
  32. 32.444 − 331 =
  33. 33.679 − 199 =
  34. 34.493 − 245 =
  35. 35.224 + 291 =
  36. 36.512 − 333 =
  37. 37.588 + 136 =
  38. 38.856 − 601 =
  39. 39.748 + 421 =
  40. 40.687 − 429 =

Answer key

  1. 647
  2. 943
  3. 971
  4. 103
  5. 369
  6. 869
  7. 1175
  8. 563
  9. 265
  10. 740
  11. 435
  12. 123
  13. 761
  14. 150
  15. 130
  16. 926
  17. 401
  18. 106
  19. 400
  20. 182
  21. 556
  22. 824
  23. 383
  24. 545
  25. 137
  26. 217
  27. 893
  28. 804
  29. 505
  30. 175
  31. 252
  32. 113
  33. 480
  34. 248
  35. 515
  36. 179
  37. 724
  38. 255
  39. 1169
  40. 258

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