Question 958740
Let {{{ x }}} = ounces of 60% chocolate needed
{{{ .6x }}} = ounces of cocoa in 60% mixture
{{{ .8*4 = 3.2 }}} ounces in 80% chocolate
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{{{ ( .6x + 3.2 ) / ( x + 4 ) = .75 }}}
{{{ .6x + 3.2 = .75*( x + 4 ) }}}
{{{ .6x + 3.2  = .75x + 3 }}}
{{{ .15x = .2 }}}
{{{ x = 1.333 }}}
1.333 ounces of 60% chocolate are needed
check:
{{{ ( .6*1.333 + 3.2 ) / ( 1.333 + 4 ) = .75 }}}
{{{ ( .8 + 3.2 ) / ( 5.333 ) = .75 }}}
{{{ 4 / ( 16/3 ) = 3/4 }}}
{{{ ( 3/16 )*4 = 12/16 }}}
{{{ 12/16 = 12/16 }}}
OK