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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 137 · 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. 1.287 + 528 =
  2. 2.280 + 311 =
  3. 3.282 + 113 =
  4. 4.878 − 539 =
  5. 5.758 − 568 =
  6. 6.812 − 198 =
  7. 7.890 − 684 =
  8. 8.598 − 188 =
  9. 9.984 − 671 =
  10. 10.865 − 615 =
  11. 11.177 + 205 =
  12. 12.472 − 274 =
  13. 13.732 + 418 =
  14. 14.656 − 395 =
  15. 15.379 + 181 =
  16. 16.720 + 517 =
  17. 17.591 + 409 =
  18. 18.236 + 167 =
  19. 19.140 + 228 =
  20. 20.787 + 256 =
  21. 21.391 + 553 =
  22. 22.697 − 588 =
  23. 23.206 + 521 =
  24. 24.689 + 539 =
  25. 25.676 + 564 =
  26. 26.423 + 157 =
  27. 27.564 − 448 =
  28. 28.533 − 284 =
  29. 29.710 − 157 =
  30. 30.832 − 508 =
  31. 31.735 + 468 =
  32. 32.242 + 345 =
  33. 33.186 + 119 =
  34. 34.669 + 146 =
  35. 35.857 − 496 =
  36. 36.666 − 132 =
  37. 37.913 − 671 =
  38. 38.534 − 229 =
  39. 39.161 + 225 =
  40. 40.179 + 244 =

Answer key

  1. 815
  2. 591
  3. 395
  4. 339
  5. 190
  6. 614
  7. 206
  8. 410
  9. 313
  10. 250
  11. 382
  12. 198
  13. 1150
  14. 261
  15. 560
  16. 1237
  17. 1000
  18. 403
  19. 368
  20. 1043
  21. 944
  22. 109
  23. 727
  24. 1228
  25. 1240
  26. 580
  27. 116
  28. 249
  29. 553
  30. 324
  31. 1203
  32. 587
  33. 305
  34. 815
  35. 361
  36. 534
  37. 242
  38. 305
  39. 386
  40. 423

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