Question 533133
Let {{{ x }}} = mg of a metal containing 45% nickel
{{{ .45x }}} = mg of pure nickel in 45% alloy
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{{{ ( .45x + 6 ) / ( x + 6 ) = .78 }}}
{{{ .45x + 6 = .78*( x + 6 ) }}}
{{{ .45x + 6 = .78x + 4.68 }}}
{{{ .78x - .45x = 6 - 4.68 }}}
{{{ .33x = 1.32 }}}
{{{ x = 4 }}}
4 mg of 45% nickel metal must be added
check:
{{{ ( .45*4 + 6 ) / ( 4 + 6 ) = .78 }}}
{{{ ( 1.8 + 6 ) / 10 = .78 }}}
{{{ 7.8 = .78*10 }}}
{{{ 7.8 = 7.8 }}}
OK