Question 625229
Let {{{ x }}} = liters of 50% acid solution needed
{{{ .5x }}} = liters of acid in 50% solution
{{{ .15*10 = 1.5 }}} liters of acid in 15% solution
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{{{ ( .5x + 1.5 ) / ( x + 10 ) = .25 }}}
{{{ .5x + 1.5 = .25*( x + 10 ) }}}
{{{ .5x + 1.5 = .25x + 2.5 }}}
{{{ .25x = 2.5 - 1.5 }}}
{{{ .25x = 1 }}}
{{{ x = 4 }}}
4 liters of 50% acid solution are needed
check:
{{{ ( .5x + 1.5 ) / ( x + 10 ) = .25 }}}
{{{ ( .5*4 + 1.5 ) / ( 4 + 10 ) = .25 }}}
{{{ 3.5 / 14 = .25 }}}
{{{ 3.5 = .25*14 }}}
{{{ 3.5 = 3.5 }}}
OK