Question 1006265
(1)
{{{ .7*7 = 4.9 }}} fl oz of sugar in the 70% solution
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The concentration is:
{{{ 4.9/( 7 + 3 ) =4.9/10 }}}
{{{ 4.9/10 = .49 }}}
{{{ .49*100 = 49 }}}
The new concentration is 49%
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(2) 
{{{ .04*12 = .48 }}} pounds of silver in 4% alloy
{{{ .28*4 = 1.12 }}} pounds of silver in 28% alloy
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the % silver is:
{{{ ( .48 + 1.12 ) / ( 12 + 4 ) }}}
{{{ 1.6 / 16 = .1 }}}
{{{ .1*100 = 10 }}}
10%