Calculating ABV after adding Liquor (MATH question)

[vast_reaction]

Hi there. I am bottling a 5 gallon batch of Milk Chocolate Stout tomorrow, and I'm adding some Jameson Irish Whiskey to it. I am trying to determine what the ABV will be after adding the Whiskey, so I know if the existing yeast will be strong enough to carbonate it. Here's the specifics of what will be in each 22oz bottle:

20 fluid ounces Beer @ 6.5% ABV
1 fluid ounce Whiskey @ 40% ABV

I suck at Math. How do you calculate the resulting ABV of this 21 fluid ounce solution? Thanks for any help with this equation!

-Matt

 

[Skaggz]

40/21 = 1.9
1.9+6.5=8.4

Should be looking at around 8.4%
if my maths are correct, that is

 

[vast_reaction]

Yeah, I just talked to my dad on the phone also. He explained it as:

6.5% Alcohol in 20oz of Beer = 1.3oz alcohol.
40% Alcohol in 1oz of Whiskey = .4oz alcohol.

1.7oz total Alcohol divided by 21oz Solution = .08, or 8% ABV.

Thanks for the help, I'm sure the yeast will be fine!