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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 403 · 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. 1.270 + 427 =
  2. 2.168 + 413 =
  3. 3.300 + 428 =
  4. 4.855 − 299 =
  5. 5.697 − 558 =
  6. 6.379 + 272 =
  7. 7.595 − 302 =
  8. 8.943 − 161 =
  9. 9.669 − 521 =
  10. 10.248 + 214 =
  11. 11.825 − 267 =
  12. 12.687 − 345 =
  13. 13.756 + 619 =
  14. 14.657 − 337 =
  15. 15.513 + 218 =
  16. 16.252 + 636 =
  17. 17.590 + 116 =
  18. 18.252 + 544 =
  19. 19.195 + 562 =
  20. 20.864 − 655 =
  21. 21.647 − 518 =
  22. 22.704 + 236 =
  23. 23.622 + 155 =
  24. 24.489 − 152 =
  25. 25.625 + 346 =
  26. 26.535 − 194 =
  27. 27.888 − 691 =
  28. 28.786 + 332 =
  29. 29.609 + 257 =
  30. 30.231 + 505 =
  31. 31.345 + 176 =
  32. 32.644 + 521 =
  33. 33.829 − 291 =
  34. 34.441 − 118 =
  35. 35.521 + 597 =
  36. 36.670 − 473 =
  37. 37.473 − 224 =
  38. 38.245 + 224 =
  39. 39.826 − 637 =
  40. 40.559 + 207 =

Answer key

  1. 697
  2. 581
  3. 728
  4. 556
  5. 139
  6. 651
  7. 293
  8. 782
  9. 148
  10. 462
  11. 558
  12. 342
  13. 1375
  14. 320
  15. 731
  16. 888
  17. 706
  18. 796
  19. 757
  20. 209
  21. 129
  22. 940
  23. 777
  24. 337
  25. 971
  26. 341
  27. 197
  28. 1118
  29. 866
  30. 736
  31. 521
  32. 1165
  33. 538
  34. 323
  35. 1118
  36. 197
  37. 249
  38. 469
  39. 189
  40. 766

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