Question 657226
Let {{{ x }}} = quarts of pure antifreeze needed
{{{ .3*2 = .6 }}} quarts of pure antifreeze in 30% solution
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{{{ ( .6 + x ) / ( 2 + x ) = .6 }}}
{{{ .6 + x = .6*( 2 + x ) }}}
{{{ .6 + x = 1.2 + .6x }}}
{{{ x - .6x = 1.2 - .6 }}}
{{{ .4x = .6 }}}
{{{ x = 3/2 }}}
1.5 quarts of pure antifreeze must be added
check:
{{{ ( .6 + x ) / ( 2 + x ) = .6 }}}
{{{ ( .6 + 1.5 ) / ( 2 + 1.5 ) = .6 }}}
{{{ 2.1 / 3.5 = .6 }}}
{{{ 2.1 = .6 * 3.5 }}}
{{{ 2.1 = 2.1 }}}
OK