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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 299 · 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. 1.247 + 311 =
  2. 2.479 + 597 =
  3. 3.151 + 378 =
  4. 4.586 + 178 =
  5. 5.978 − 555 =
  6. 6.271 + 253 =
  7. 7.175 + 646 =
  8. 8.621 + 216 =
  9. 9.677 − 541 =
  10. 10.129 + 481 =
  11. 11.672 + 441 =
  12. 12.847 − 678 =
  13. 13.612 + 112 =
  14. 14.679 + 612 =
  15. 15.661 − 353 =
  16. 16.529 − 368 =
  17. 17.916 − 279 =
  18. 18.232 + 126 =
  19. 19.677 − 375 =
  20. 20.310 + 208 =
  21. 21.634 − 262 =
  22. 22.628 − 231 =
  23. 23.742 + 427 =
  24. 24.465 − 127 =
  25. 25.843 − 184 =
  26. 26.817 − 155 =
  27. 27.375 + 478 =
  28. 28.581 + 435 =
  29. 29.787 + 302 =
  30. 30.558 + 419 =
  31. 31.466 − 337 =
  32. 32.473 − 373 =
  33. 33.690 + 614 =
  34. 34.757 + 141 =
  35. 35.616 − 259 =
  36. 36.146 + 184 =
  37. 37.786 − 486 =
  38. 38.501 + 258 =
  39. 39.491 − 232 =
  40. 40.529 − 296 =

Answer key

  1. 558
  2. 1076
  3. 529
  4. 764
  5. 423
  6. 524
  7. 821
  8. 837
  9. 136
  10. 610
  11. 1113
  12. 169
  13. 724
  14. 1291
  15. 308
  16. 161
  17. 637
  18. 358
  19. 302
  20. 518
  21. 372
  22. 397
  23. 1169
  24. 338
  25. 659
  26. 662
  27. 853
  28. 1016
  29. 1089
  30. 977
  31. 129
  32. 100
  33. 1304
  34. 898
  35. 357
  36. 330
  37. 300
  38. 759
  39. 259
  40. 233

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