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Sum of 1 to 100 Worksheet

Maths tricks trick 8: Add 1 to 100 in seconds · Set 540 · 40 questions
TalentJR

The trick (Pairs): Pair the first and last numbers: each pair adds to n + 1. Count the pairs — or multiply n × (n + 1) and halve it. Odd numbers 1 + 3 + 5 + …: count them and multiply that count by itself.

NameDateTime takenScore ___ / 40
  1. 1.1 + 3 + 5 + … + 39 =
  2. 2.1 + 3 + 5 + … + 31 =
  3. 3.1 + 3 + 5 + … + 25 =
  4. 4.1 + 3 + 5 + … + 21 =
  5. 5.1 + 2 + 3 + … + 28 =
  6. 6.1 + 2 + 3 + … + 94 =
  7. 7.1 + 3 + 5 + … + 9 =
  8. 8.1 + 3 + 5 + … + 15 =
  9. 9.1 + 2 + 3 + … + 54 =
  10. 10.1 + 3 + 5 + … + 23 =
  11. 11.1 + 2 + 3 + … + 73 =
  12. 12.1 + 3 + 5 + … + 17 =
  13. 13.1 + 2 + 3 + … + 21 =
  14. 14.1 + 2 + 3 + … + 98 =
  15. 15.1 + 2 + 3 + … + 79 =
  16. 16.1 + 3 + 5 + … + 27 =
  17. 17.1 + 3 + 5 + … + 29 =
  18. 18.1 + 2 + 3 + … + 97 =
  19. 19.1 + 2 + 3 + … + 11 =
  20. 20.1 + 2 + 3 + … + 69 =
  21. 21.1 + 2 + 3 + … + 12 =
  22. 22.1 + 2 + 3 + … + 68 =
  23. 23.1 + 2 + 3 + … + 49 =
  24. 24.1 + 3 + 5 + … + 19 =
  25. 25.1 + 3 + 5 + … + 45 =
  26. 26.1 + 2 + 3 + … + 72 =
  27. 27.1 + 3 + 5 + … + 33 =
  28. 28.1 + 2 + 3 + … + 24 =
  29. 29.1 + 2 + 3 + … + 83 =
  30. 30.1 + 3 + 5 + … + 43 =
  31. 31.1 + 2 + 3 + … + 87 =
  32. 32.1 + 2 + 3 + … + 20 =
  33. 33.1 + 2 + 3 + … + 71 =
  34. 34.1 + 2 + 3 + … + 70 =
  35. 35.1 + 2 + 3 + … + 13 =
  36. 36.1 + 2 + 3 + … + 80 =
  37. 37.1 + 2 + 3 + … + 9 =
  38. 38.1 + 2 + 3 + … + 61 =
  39. 39.1 + 2 + 3 + … + 89 =
  40. 40.1 + 2 + 3 + … + 18 =

Answer key

  1. 400
  2. 256
  3. 169
  4. 121
  5. 406
  6. 4465
  7. 25
  8. 64
  9. 1485
  10. 144
  11. 2701
  12. 81
  13. 231
  14. 4851
  15. 3160
  16. 196
  17. 225
  18. 4753
  19. 66
  20. 2415
  21. 78
  22. 2346
  23. 1225
  24. 100
  25. 529
  26. 2628
  27. 289
  28. 300
  29. 3486
  30. 484
  31. 3828
  32. 210
  33. 2556
  34. 2485
  35. 91
  36. 3240
  37. 45
  38. 1891
  39. 4005
  40. 171

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