Question 155816

Let x=amount of 32% silver alloy needed

Now we know that the amount of pure silver in the 32% alloy (0.32x) plus the amount of pure silver in the 48% alloy (0.48*25) has to equal the amount of pure silver in the final mixture(0.42*(25+x)).  So our equation to solve is:

0.32x+0.48*25=0.42(25+x)  get rid of parens and simplify

0.32x+12=10.5+0.42x  subtract 0.32x and also 10.5 from each side

0.32x-0.32x+12-10.5=10.5-10.5+0.42x-0.32x  collect like terms

0.10x=1.5  divide each side by 0.10
x=15 lb----------------------------amount of 32% silver alloy needed

CK
0.32*15+0.48*25=0.42*40
4.8+12=16.8
16.8=16.8

Hope this helps----ptaylor