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Sum of 1 to 100 Worksheet

Maths tricks trick 8: Add 1 to 100 in seconds · Set 942 · 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 + 2 + 3 + … + 49 =
  3. 3.1 + 3 + 5 + … + 37 =
  4. 4.1 + 2 + 3 + … + 27 =
  5. 5.1 + 3 + 5 + … + 27 =
  6. 6.1 + 2 + 3 + … + 41 =
  7. 7.1 + 2 + 3 + … + 39 =
  8. 8.1 + 2 + 3 + … + 73 =
  9. 9.1 + 3 + 5 + … + 43 =
  10. 10.1 + 2 + 3 + … + 70 =
  11. 11.1 + 2 + 3 + … + 6 =
  12. 12.1 + 3 + 5 + … + 41 =
  13. 13.1 + 2 + 3 + … + 8 =
  14. 14.1 + 2 + 3 + … + 61 =
  15. 15.1 + 2 + 3 + … + 50 =
  16. 16.1 + 3 + 5 + … + 11 =
  17. 17.1 + 3 + 5 + … + 19 =
  18. 18.1 + 2 + 3 + … + 74 =
  19. 19.1 + 2 + 3 + … + 28 =
  20. 20.1 + 2 + 3 + … + 16 =
  21. 21.1 + 2 + 3 + … + 26 =
  22. 22.1 + 2 + 3 + … + 65 =
  23. 23.1 + 2 + 3 + … + 14 =
  24. 24.1 + 2 + 3 + … + 83 =
  25. 25.1 + 2 + 3 + … + 96 =
  26. 26.1 + 2 + 3 + … + 67 =
  27. 27.1 + 2 + 3 + … + 72 =
  28. 28.1 + 2 + 3 + … + 69 =
  29. 29.1 + 2 + 3 + … + 54 =
  30. 30.1 + 2 + 3 + … + 93 =
  31. 31.1 + 2 + 3 + … + 75 =
  32. 32.1 + 2 + 3 + … + 25 =
  33. 33.1 + 2 + 3 + … + 21 =
  34. 34.1 + 2 + 3 + … + 11 =
  35. 35.1 + 3 + 5 + … + 31 =
  36. 36.1 + 2 + 3 + … + 97 =
  37. 37.1 + 2 + 3 + … + 51 =
  38. 38.1 + 2 + 3 + … + 9 =
  39. 39.1 + 3 + 5 + … + 9 =
  40. 40.1 + 2 + 3 + … + 37 =

Answer key

  1. 400
  2. 1225
  3. 361
  4. 378
  5. 196
  6. 861
  7. 780
  8. 2701
  9. 484
  10. 2485
  11. 21
  12. 441
  13. 36
  14. 1891
  15. 1275
  16. 36
  17. 100
  18. 2775
  19. 406
  20. 136
  21. 351
  22. 2145
  23. 105
  24. 3486
  25. 4656
  26. 2278
  27. 2628
  28. 2415
  29. 1485
  30. 4371
  31. 2850
  32. 325
  33. 231
  34. 66
  35. 256
  36. 4753
  37. 1326
  38. 45
  39. 25
  40. 703

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