Question 297117
Let {{{x}}} = liters of 40% solution needed
Let {{{y}}} = liters of 60% solution you end up with
given:
(1) {{{y = x + 10}}}
(2) {{{(.4x + .8*10)/y = .6}}}
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from (2),
(2) {{{.4x + .8*10 = .6y}}}
{{{6y = 4x + 80}}}
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{{{y = (2/3)*x + 40/3}}}
and
{{{y = x + 10}}} answers
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check answers:
{{{(2/3)*x + 40/3 = x + 10}}}
{{{2x + 40 = 3x + 30}}}
{{{x = 10}}}
and, since
{{{y = x + 10}}}
{{{y = 20}}}
(2) {{{(.4x + .8*10)/y = .6}}}
(2) {{{(.4*10 + .8*10)/20 = .6}}}
{{{(4 + 8)/20 = .6}}}
{{{12/20 = .6}}}
{{{12 = 12}}}
OK