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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 378 · 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. 1.301 + 493 =
  2. 2.925 − 435 =
  3. 3.322 + 371 =
  4. 4.902 − 141 =
  5. 5.508 + 351 =
  6. 6.595 − 467 =
  7. 7.675 − 495 =
  8. 8.442 + 219 =
  9. 9.176 + 445 =
  10. 10.762 + 133 =
  11. 11.137 + 683 =
  12. 12.488 + 309 =
  13. 13.762 − 164 =
  14. 14.865 − 211 =
  15. 15.507 − 296 =
  16. 16.270 + 332 =
  17. 17.568 − 156 =
  18. 18.592 − 173 =
  19. 19.553 − 428 =
  20. 20.226 + 576 =
  21. 21.440 − 309 =
  22. 22.751 + 663 =
  23. 23.725 + 471 =
  24. 24.779 − 623 =
  25. 25.739 + 277 =
  26. 26.720 − 281 =
  27. 27.176 + 229 =
  28. 28.361 + 359 =
  29. 29.547 − 371 =
  30. 30.489 − 249 =
  31. 31.917 − 652 =
  32. 32.510 + 236 =
  33. 33.297 + 473 =
  34. 34.662 − 163 =
  35. 35.604 − 298 =
  36. 36.485 − 357 =
  37. 37.598 − 352 =
  38. 38.547 − 292 =
  39. 39.856 − 221 =
  40. 40.351 + 409 =

Answer key

  1. 794
  2. 490
  3. 693
  4. 761
  5. 859
  6. 128
  7. 180
  8. 661
  9. 621
  10. 895
  11. 820
  12. 797
  13. 598
  14. 654
  15. 211
  16. 602
  17. 412
  18. 419
  19. 125
  20. 802
  21. 131
  22. 1414
  23. 1196
  24. 156
  25. 1016
  26. 439
  27. 405
  28. 720
  29. 176
  30. 240
  31. 265
  32. 746
  33. 770
  34. 499
  35. 306
  36. 128
  37. 246
  38. 255
  39. 635
  40. 760

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