Question 1005947
Let {{{ x }}} = grams of 38% gold needed
{{{ .38x }}} = grams of gold in 38% gold
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{{{ ( .38x + 3 ) / ( x + 3 ) = .78 }}}
{{{ .38x + 3 = .78*( x + 3 ) }}}
{{{ .38x + 3 = .78x + 2.34 }}}
{{{ .4x = .66 }}}
{{{ x = 1.65 }}}
1.65 grams of 38% gold are needed
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check:
{{{ ( .38x + 3 ) / ( x + 3 ) = .78 }}}
{{{ ( .38*1.65 + 3 ) / ( 1.65 + 3 ) = .78 }}}
{{{ ( .627 + 3 ) / 4.65 = .78 }}}
{{{ 3.627 = 3.627 }}}
OK