Question 1030023
I don't know the 6 step method, but
this is how I do it:
Let {{{ x }}} = gallons of 60% antifreeze solution needed
{{{ .6x }}} = gallons of pure antifreeze in the 60% solution
{{{ .2*60 = 12 }}} gallons of pure antifreeze in 20% solution
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{{{ ( .6x + 12 ) / ( x + 60 ) = .5 }}}
{{{ .6x + 12 = .5*( x + 60 ) }}}
{{{ .6x + 12 = .5x + 30 }}}
{{{ .1x = 18 }}}
{{{ x = 180 }}}
180 gallons of 60% solution are needed
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check answer:
{{{ ( .6x + 12 ) / ( x + 60 ) = .5 }}}
{{{ ( .6*180 + 12 ) / ( 180 + 60 ) = .5 }}}
{{{ ( 108 + 12 ) / 240 = .5 }}}
{{{ 120 = .5*240 }}}
{{{ 120 = 120 }}}
OK