Question 125402
(acid from each solution) / (total amount of solution) = 35%
Let {{{a}}}= amount of 25% solution used
Let {{{b}}}= amount of 50% solution used
{{{(.25a + .5b) / (a + b) = .35}}}
also given is
{{{a + b = 200}}} ml
{{{b = 200 - a}}}
{{{(.25a + .5b) / 200 = .35}}}
{{{(.25a + .5(200 - a)) / 200 = .35}}}
{{{(.25a + 100 - .5a) / 200 = .35}}}
{{{(-.25a + 100) / 200 = .35}}}
{{{-.25a + 100 = 70}}}
{{{-.25a = -30}}}
{{{a = 120}}}
{{{b = 200 - a}}}
{{{b = 200 - 120}}}
{{{b = 80}}}
There are 120 ml of the 25% solution and 80 ml of the 50% solution
check answer
{{{(.25a + .5b) / 200 = .35}}}
{{{(.25*120 + .5*80) / 200 = .35}}}
{{{(30 + 40) / 200 = .35}}}
{{{7/20 = .35}}}
{{{.35 = .35}}}
OK