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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 997 · 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. 1.205 + 374 =
  2. 2.227 + 283 =
  3. 3.970 − 546 =
  4. 4.722 + 286 =
  5. 5.786 − 138 =
  6. 6.780 + 255 =
  7. 7.244 + 291 =
  8. 8.460 − 186 =
  9. 9.534 − 131 =
  10. 10.627 + 395 =
  11. 11.453 − 304 =
  12. 12.721 − 508 =
  13. 13.498 + 451 =
  14. 14.633 − 502 =
  15. 15.568 − 258 =
  16. 16.175 + 509 =
  17. 17.621 − 229 =
  18. 18.817 − 578 =
  19. 19.615 − 485 =
  20. 20.876 − 494 =
  21. 21.975 − 838 =
  22. 22.733 − 393 =
  23. 23.375 + 419 =
  24. 24.339 + 471 =
  25. 25.245 + 128 =
  26. 26.416 − 145 =
  27. 27.462 − 231 =
  28. 28.145 + 527 =
  29. 29.710 − 144 =
  30. 30.805 − 312 =
  31. 31.810 − 692 =
  32. 32.875 − 423 =
  33. 33.619 + 243 =
  34. 34.490 − 236 =
  35. 35.267 + 659 =
  36. 36.712 − 445 =
  37. 37.686 − 211 =
  38. 38.850 − 533 =
  39. 39.508 + 295 =
  40. 40.432 − 243 =

Answer key

  1. 579
  2. 510
  3. 424
  4. 1008
  5. 648
  6. 1035
  7. 535
  8. 274
  9. 403
  10. 1022
  11. 149
  12. 213
  13. 949
  14. 131
  15. 310
  16. 684
  17. 392
  18. 239
  19. 130
  20. 382
  21. 137
  22. 340
  23. 794
  24. 810
  25. 373
  26. 271
  27. 231
  28. 672
  29. 566
  30. 493
  31. 118
  32. 452
  33. 862
  34. 254
  35. 926
  36. 267
  37. 475
  38. 317
  39. 803
  40. 189

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