Is this math correct?

[Aheadatime]

I've grown used to the Wizard Labs 10% Menthol Solution, but wanted to get it cheaper without mixing my own crystals. I ordered some TFA Menthol (PG), but this is mixed at 66% strength. I did some basic math to dilute it properly, but wanted it double checked.
I have 15mls of 66% menthol, and I wanted xmLs of 10% menthol, so


.66(15) = .10(x)

9.9 = .10(x)

9.9 = .10(99)

So I need 99mLs total to reach a 10% strength, meaning I need to add 99mLs minus the original 15mLs of PG which equals 84. I should take my 15mLs of 66% solution and add 84mLs of PG to reach the 10% solution correct?

 

[MarkyD]

Yeah that looks right... another way to do this is to simply scale strength1/strength2 and multiply by the quantity of solution1 to get the quantity of solution2 needed...

66/10 = 6.6 (solution1 is 6.6 times stronger than solution2)

15*6.6 = 99 (quantity of solution2 needed to dilute strength of solution1 6.6 times)

99-15 = 84ml (subtract quantity of solution1 to get quantity of dilutant to add)

 

[spaceballsrules]

Yup, that is correct.

1/6.6=15/99

 

[Aheadatime]

Thanks guys, I appreciate it. I've mixed it and will wait a day or so before using it to let it sort of 'steep'.