Question 1022164
Let {{{ x }}} = grams of gold to be added
{{{ .3*500 = 150 }}} grams of gold in 30% alloy
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{{{ ( x + 150 ) / ( x + 500 ) = .4 }}}
{{{ x + 150 = .4*( x + 500 ) }}}
{{{ x + 150 = .4x +200 }}}
{{{ .6x = 50 }}}
{{{ x = 83.333 }}}
83 and 1/3 grams of gold must be added
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check:
{{{ ( x + 150 ) / ( x + 500 ) = .4 }}}
{{{ ( 83.333 + 150 ) / ( 83.333 + 500 ) = .4 }}}
{{{ 233.333 / 583.333 = .4 }}}
{{{ .3999997 = .4 }}}
error due to rounding off
OK