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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 510 · 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. 1.400 + 245 =
  2. 2.447 + 689 =
  3. 3.320 + 261 =
  4. 4.222 + 619 =
  5. 5.420 − 276 =
  6. 6.496 − 112 =
  7. 7.660 + 223 =
  8. 8.664 + 335 =
  9. 9.474 − 231 =
  10. 10.585 + 499 =
  11. 11.841 − 275 =
  12. 12.715 + 112 =
  13. 13.849 − 406 =
  14. 14.164 + 194 =
  15. 15.606 + 163 =
  16. 16.904 − 538 =
  17. 17.613 − 215 =
  18. 18.471 + 141 =
  19. 19.551 + 645 =
  20. 20.539 + 651 =
  21. 21.487 − 271 =
  22. 22.346 + 299 =
  23. 23.643 − 376 =
  24. 24.676 + 501 =
  25. 25.207 + 494 =
  26. 26.983 − 183 =
  27. 27.284 + 151 =
  28. 28.494 + 337 =
  29. 29.370 + 135 =
  30. 30.664 + 262 =
  31. 31.958 − 384 =
  32. 32.794 − 561 =
  33. 33.937 − 445 =
  34. 34.137 + 485 =
  35. 35.691 + 568 =
  36. 36.562 + 565 =
  37. 37.312 + 381 =
  38. 38.308 + 384 =
  39. 39.927 − 811 =
  40. 40.428 + 535 =

Answer key

  1. 645
  2. 1136
  3. 581
  4. 841
  5. 144
  6. 384
  7. 883
  8. 999
  9. 243
  10. 1084
  11. 566
  12. 827
  13. 443
  14. 358
  15. 769
  16. 366
  17. 398
  18. 612
  19. 1196
  20. 1190
  21. 216
  22. 645
  23. 267
  24. 1177
  25. 701
  26. 800
  27. 435
  28. 831
  29. 505
  30. 926
  31. 574
  32. 233
  33. 492
  34. 622
  35. 1259
  36. 1127
  37. 693
  38. 692
  39. 116
  40. 963

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