Question 264027
In words:
(liters of alcohol in final solution)/(total liters of final solution) = 50%
In 25 liters of a 26% solution, liters of alcohol =
{{{.26*25 = 6.5}}} liters
Let {{{x}}} = liters of pure alcohol to be added
{{{(x + 6.5)/(25 + x) = .5}}}
{{{x + 6.5 = .5*(25 + x)}}}
{{{x + 6.5 = 25/2 +x/2}}}
{{{2x + 13 = 25 + x}}}
{{{x = 12}}}
12 liters of pure alcohol must be added
check answer:
{{{(x + 6.5)/(25 + x) = .5}}}
{{{(12 + 6.5)/(25 + 12) = .5}}}
{{{18.5/37 = .5}}}
{{{18.5 = 18.5}}}
OK