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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 420 · 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. 1.261 + 332 =
  2. 2.223 + 133 =
  3. 3.721 − 296 =
  4. 4.627 + 492 =
  5. 5.648 + 527 =
  6. 6.718 + 145 =
  7. 7.176 + 518 =
  8. 8.499 + 485 =
  9. 9.552 + 153 =
  10. 10.667 − 242 =
  11. 11.201 + 211 =
  12. 12.519 + 544 =
  13. 13.495 + 646 =
  14. 14.807 − 526 =
  15. 15.593 − 263 =
  16. 16.936 − 652 =
  17. 17.748 − 643 =
  18. 18.429 − 272 =
  19. 19.759 − 501 =
  20. 20.274 + 621 =
  21. 21.197 + 428 =
  22. 22.440 − 251 =
  23. 23.180 + 145 =
  24. 24.447 + 134 =
  25. 25.743 + 496 =
  26. 26.421 + 195 =
  27. 27.652 + 391 =
  28. 28.346 + 681 =
  29. 29.153 + 508 =
  30. 30.202 + 642 =
  31. 31.428 − 172 =
  32. 32.452 − 231 =
  33. 33.679 − 172 =
  34. 34.473 − 366 =
  35. 35.958 − 801 =
  36. 36.701 + 552 =
  37. 37.852 − 457 =
  38. 38.613 − 282 =
  39. 39.555 + 253 =
  40. 40.501 − 204 =

Answer key

  1. 593
  2. 356
  3. 425
  4. 1119
  5. 1175
  6. 863
  7. 694
  8. 984
  9. 705
  10. 425
  11. 412
  12. 1063
  13. 1141
  14. 281
  15. 330
  16. 284
  17. 105
  18. 157
  19. 258
  20. 895
  21. 625
  22. 189
  23. 325
  24. 581
  25. 1239
  26. 616
  27. 1043
  28. 1027
  29. 661
  30. 844
  31. 256
  32. 221
  33. 507
  34. 107
  35. 157
  36. 1253
  37. 395
  38. 331
  39. 808
  40. 297

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