Question 157305
First of all, this might be a "trick" question. It talks about acid
solutions giving an alcohol solution. Maybe it's miscopied someway.
Let {{{x}}}= liters of 70% solution needed
In words:
(alcohol in 70% solution + alcohol in 10% solution) / (total solution) = 25%
{{{(.7x + .1*18) / (x + 18) = .25}}}
multiply both sides by {{{x+18}}}
{{{.7x + 1.8 = .25*(x + 18)}}}
{{{.7x + 1.8 = .25x + 4.5}}}
{{{.45x = 2.7}}}
{{{x = 6}}} liters of 70% solution needed
check:
{{{(.7x + .1*18) / (x + 18) = .25}}}
{{{(.7*6 + .1*18) / (6 + 18) = .25}}}
{{{(4.2 + 1.8) / 24 = .25}}}
{{{6/24 = .25}}}
{{{.25 = .25}}}
OK