Question 892994
Let {{{ x }}} = gallons of 60% solution needed
{{{ .6x }}} = gallons of concentrate in 60% solution
{{{ .1*30 = 3 }}} = gallons of concentrate in 10% solution
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{{{ ( .6x + 3 ) / ( x + 30 ) = .4 }}}
{{{ .6x + 3 = .4*( x + 30 ) }}}
{{{ .6x + 3 = .4x + 12 }}}
{{{ .2x = 9 }}}
{{{ x = 45 }}}
45 gallons of 60% solution must be added
check:
{{{ ( .6x + 3 ) / ( x + 30 ) = .4 }}}
{{{ ( .6*45 + 3 ) / ( 45 + 30 ) = .4 }}}
{{{ ( 27 + 3 ) / 75 = .4 }}}
{{{ 30 = .4*75 }}}
{{{ 30 = 30 }}}
OK