Question 587821
Let {{{x}}} = liters of 40% solution needed
{{{ .7*60 = 42 }}} liters
given:
{{{ ( .4x + 42 ) / ( x + 60 ) = .5 }}}
{{{ .4x + 42 = .5*( x + 60 ) }}}
{{{ .4x + 42 = .5x + 30 }}}
{{{ .1x = 12 }}}
{{{ x = 120 }}}
120 liters of the 40% solution are needed