psych said:

You are probably right about the trade Krischan.

About the average to get a 35%fcr spirit shouldn't that be 5.5 spirit packs and 5 hels?

There is a 1 in 11 chance to roll a 35% so he's basing his answer on if you roll 11 times you have an average chance to roll a 35%FCR spirit.

Which is semi-true.

You have a 9.1%chance to roll a 35% spirit, meaning you ahve a 91% chance to NOT roll one.

To work out the odds of rolling a 35% after X rolls you work out the chance of NOT rolling and subtract that from 1.

e.g:

3 rolls. Chance to NOT get 35% = (0.91)^3. Chance to get 35% = 1-(0.91)^3 = 25%

5 rolls. Chance to NOT get 35% = (0.91)^5. Chance to get 35% = (1-0.91)^5 = 38%

10 rolls.Chance to NOT get 35% = (0.91)^10. Chance to get 35% = (1-0.91)^10 = 61%

To have a 50% chance to have rolled one you need (1-0.91)^x = 0.5, so for 50% chance you need to make 7.5rolls.

This is just for one, over a long time when you ahve gotten MANY spirits from re-rolling the average will be 11 rolls per 35%, as the rolls you save from a spirit rolled on a first attempt (9% chance) cancel out the runes you spend rolling one on your 25th attempt (9% chance again) and so on for other successful attempt combinations.