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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 252 · 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. 1.653 + 676 =
  2. 2.448 + 137 =
  3. 3.239 + 387 =
  4. 4.532 − 293 =
  5. 5.415 + 572 =
  6. 6.236 + 526 =
  7. 7.598 + 154 =
  8. 8.255 + 131 =
  9. 9.684 − 503 =
  10. 10.578 − 396 =
  11. 11.443 + 245 =
  12. 12.454 + 262 =
  13. 13.550 + 387 =
  14. 14.574 + 202 =
  15. 15.531 − 264 =
  16. 16.641 − 498 =
  17. 17.188 + 577 =
  18. 18.135 + 158 =
  19. 19.353 + 644 =
  20. 20.782 − 479 =
  21. 21.629 + 334 =
  22. 22.195 + 314 =
  23. 23.678 − 307 =
  24. 24.551 + 224 =
  25. 25.492 − 346 =
  26. 26.786 − 171 =
  27. 27.936 − 732 =
  28. 28.461 − 159 =
  29. 29.186 + 382 =
  30. 30.836 − 535 =
  31. 31.203 + 276 =
  32. 32.280 + 671 =
  33. 33.962 − 777 =
  34. 34.345 + 545 =
  35. 35.616 − 486 =
  36. 36.410 + 113 =
  37. 37.564 − 313 =
  38. 38.879 − 715 =
  39. 39.458 + 629 =
  40. 40.428 − 186 =

Answer key

  1. 1329
  2. 585
  3. 626
  4. 239
  5. 987
  6. 762
  7. 752
  8. 386
  9. 181
  10. 182
  11. 688
  12. 716
  13. 937
  14. 776
  15. 267
  16. 143
  17. 765
  18. 293
  19. 997
  20. 303
  21. 963
  22. 509
  23. 371
  24. 775
  25. 146
  26. 615
  27. 204
  28. 302
  29. 568
  30. 301
  31. 479
  32. 951
  33. 185
  34. 890
  35. 130
  36. 523
  37. 251
  38. 164
  39. 1087
  40. 242

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