"Calculating E.D.N.A." Topic

EDNA in this case stands for Ever Decreasing Number Allocation (I think) and is found in Troops Weapons and Tactics. I want to steal the idea, but have no idea how to calculate it.

I will assume D6, but if there is a universal allocation please feel free to note it.

A weapon with limited uses is given an EDNA. After firing this weapon, the player rolls a die. If it is more* than the EDNA, the EDNA decreases by 1. If/when it hits zero, then the ammo is all gone.

I know that it might mean the weapon never runs out if all the die rolls are 1, but how do I work out a reasonable EDNA?

Thanks

*Might be equal or more than, which changes the dynamic at '1'.

Not being a mathematician, I would brute force it.
Open Excel (or google spreadsheet), Type your die rolls in one column and play with formulas in other columns.

ie:
on 1d6 (first turn), with an EDNA = 4, there is a 33% chance of running out of ammo.
Second turn, it's 50%
Third turn, it's 66%
Fourth turn, it's 83%
and the fifth turn, it's 100%

Duh, I just figured out that your chance of running out of ammo increases by 16.5% each roll. That doesn't change no matter where your EDNA starts (it's a d6, target roll decreasing by 1 each time). The EDNA affects the starting point (first roll): 16, 33, 50, 66, 83, 100

Not quite. Stryderg's calculations assumes you fail every roll such that your EDNA reduces each time. That is, in his example, on the second roll there is a 50% chance of failing the second roll ONLY if you failed the first roll, but an unchanged 33% chance failing the second roll if your first roll was successful.
If you really need more let me have your email and I'll send you a quick calculator if someone else hasn't already done so.

My calculations work just fine!! … for what I thought you wanted. Opps, I misunderstood the requirements. <mumble stupid reading comprehension grumble> :)

My gmail is Last.Hussar (at) gmail.com (!), thanks.

Initially I'm looking at smoke for 2" mortar. I want maybe an average of 8 or 9 shots I think.

Stryderg, don't worry about it!

I'll get on it – I saved your address I recommend you now delete it.

Billy, I was going to leave the spreadsheet until tomorrow, hence my email reply, but maths is sexy so I started playing…

Now torn between >=5 and >4.

Thanks, its a wonderful little tool.