Question 126568
In words:
(amount of alcohol needed) / (total amount of solution) = 20%
In the 12% solution I have
{{{12*.12 = 1.44}}}liters alcohol
Let {{{x}}} be the amount of 20% solution needed
{{{(1.44 + .2x) / (12 + x) = .14}}}
{{{1.44 + .2x = .14(12 + x)}}}
{{{1.44 + .2x = 1.68 + .14x}}}
{{{.06x = .24}}}
{{{x = 4}}}
4 liters of the 20% solution are needed
check
{{{(1.44 + .2x) / (12 + x) = .14}}}
{{{(1.44 + .2*4) / (12 + 4) = .14}}}
{{{(1.44 + .8) / 16 = .14}}}
{{{2.24 / 16 = .14}}}
{{{.14 = .14}}}
OK