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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 166 · 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 + 188 =
  2. 2.643 + 176 =
  3. 3.487 + 679 =
  4. 4.352 + 301 =
  5. 5.798 − 232 =
  6. 6.789 + 639 =
  7. 7.238 + 182 =
  8. 8.480 − 275 =
  9. 9.789 + 381 =
  10. 10.123 + 545 =
  11. 11.440 − 231 =
  12. 12.125 + 383 =
  13. 13.406 + 511 =
  14. 14.438 + 364 =
  15. 15.382 + 663 =
  16. 16.826 − 694 =
  17. 17.455 − 324 =
  18. 18.155 + 384 =
  19. 19.572 − 164 =
  20. 20.666 − 268 =
  21. 21.179 + 251 =
  22. 22.931 − 157 =
  23. 23.248 + 557 =
  24. 24.272 + 231 =
  25. 25.480 − 321 =
  26. 26.677 − 158 =
  27. 27.770 + 493 =
  28. 28.510 − 377 =
  29. 29.473 + 273 =
  30. 30.263 + 435 =
  31. 31.188 + 488 =
  32. 32.674 − 366 =
  33. 33.825 − 298 =
  34. 34.611 − 325 =
  35. 35.570 − 145 =
  36. 36.509 − 155 =
  37. 37.154 + 352 =
  38. 38.157 + 135 =
  39. 39.383 + 566 =
  40. 40.232 + 136 =

Answer key

  1. 464
  2. 819
  3. 1166
  4. 653
  5. 566
  6. 1428
  7. 420
  8. 205
  9. 1170
  10. 668
  11. 209
  12. 508
  13. 917
  14. 802
  15. 1045
  16. 132
  17. 131
  18. 539
  19. 408
  20. 398
  21. 430
  22. 774
  23. 805
  24. 503
  25. 159
  26. 519
  27. 1263
  28. 133
  29. 746
  30. 698
  31. 676
  32. 308
  33. 527
  34. 286
  35. 425
  36. 354
  37. 506
  38. 292
  39. 949
  40. 368

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