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Sum of 1 to 100 Worksheet

Maths tricks trick 8: Add 1 to 100 in seconds · Set 91 · 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 + 2 + 3 + … + 77 =
  2. 2.1 + 2 + 3 + … + 89 =
  3. 3.1 + 2 + 3 + … + 69 =
  4. 4.1 + 3 + 5 + … + 17 =
  5. 5.1 + 3 + 5 + … + 11 =
  6. 6.1 + 3 + 5 + … + 35 =
  7. 7.1 + 3 + 5 + … + 43 =
  8. 8.1 + 2 + 3 + … + 52 =
  9. 9.1 + 3 + 5 + … + 25 =
  10. 10.1 + 2 + 3 + … + 71 =
  11. 11.1 + 2 + 3 + … + 8 =
  12. 12.1 + 2 + 3 + … + 80 =
  13. 13.1 + 2 + 3 + … + 100 =
  14. 14.1 + 2 + 3 + … + 10 =
  15. 15.1 + 3 + 5 + … + 39 =
  16. 16.1 + 2 + 3 + … + 6 =
  17. 17.1 + 2 + 3 + … + 25 =
  18. 18.1 + 2 + 3 + … + 20 =
  19. 19.1 + 3 + 5 + … + 19 =
  20. 20.1 + 3 + 5 + … + 47 =
  21. 21.1 + 3 + 5 + … + 37 =
  22. 22.1 + 3 + 5 + … + 9 =
  23. 23.1 + 2 + 3 + … + 9 =
  24. 24.1 + 2 + 3 + … + 59 =
  25. 25.1 + 2 + 3 + … + 73 =
  26. 26.1 + 2 + 3 + … + 63 =
  27. 27.1 + 2 + 3 + … + 36 =
  28. 28.1 + 3 + 5 + … + 33 =
  29. 29.1 + 2 + 3 + … + 15 =
  30. 30.1 + 3 + 5 + … + 23 =
  31. 31.1 + 2 + 3 + … + 61 =
  32. 32.1 + 3 + 5 + … + 45 =
  33. 33.1 + 2 + 3 + … + 27 =
  34. 34.1 + 2 + 3 + … + 7 =
  35. 35.1 + 2 + 3 + … + 99 =
  36. 36.1 + 2 + 3 + … + 21 =
  37. 37.1 + 2 + 3 + … + 94 =
  38. 38.1 + 2 + 3 + … + 29 =
  39. 39.1 + 2 + 3 + … + 43 =
  40. 40.1 + 3 + 5 + … + 21 =

Answer key

  1. 3003
  2. 4005
  3. 2415
  4. 81
  5. 36
  6. 324
  7. 484
  8. 1378
  9. 169
  10. 2556
  11. 36
  12. 3240
  13. 5050
  14. 55
  15. 400
  16. 21
  17. 325
  18. 210
  19. 100
  20. 576
  21. 361
  22. 25
  23. 45
  24. 1770
  25. 2701
  26. 2016
  27. 666
  28. 289
  29. 120
  30. 144
  31. 1891
  32. 529
  33. 378
  34. 28
  35. 4950
  36. 231
  37. 4465
  38. 435
  39. 946
  40. 121

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