Equation to tell you your chances of getting the chance you want after x rolls. Set ‘a’ to the decimal or fraction chance you’re rolling for.

I see a lot of confusion around rng and thought this could be helpful for that. Note that this does not say "your xth roll has a y percent chance of the desired outcome" rather it says "doing x rolls has a y percent chance of the desired outcome." the example shown uses the drop rate of the rod of discord in expert mode.