Measuring Alc content when mixed in keg

[gad]

Hi Guys

Looking for a bit of help. Trying to find out how to measure the alcohol strength of keg mixture.
I have mixed 3L of Johnny Jogger Whiskey (which was 40% alc/cont pre-mix), 6L of Zero coke & 8L of water; force carbonated.
Hoping someone knows a simple way to work out what the final alc/cont is?

In my slightly inebriated state last night I managed to work it out to be 7.06% but have no idea if that is right or not.
I think I worked that out like.....
Total mix = 17L therefore 3L (whiskey) = app. 17.65%
17.65 x 40% = 7.06%

Somehow, I don't think that's right!

Can anyone set me on the right path, many thanks.

[timmy]

Looks right to me

[lethaldog]

Your pretty close to the mark there, the way i would work it out is

3 L of 40% = 3 x 40 = 120 then divide by the alc % that you desire and this will give your end volume for you so for 17.65L it would go like this..
3 x 40 = 120 then the way i worked it out was at about 6.8% divide 120 by 6.8 and you get 17.647 so the alc% of your keg is 6.8%