<PRE><B>Question 782314</B>
British sterling silver is a copper-silver alloy that is 7.5% copper by weight.
 How many grams of pure copper and how many grams of British sterling silver should be used to prepare 190 grams of a copper-silver alloy that is 18% copper by weight? 
:
let x = the amt of pure copper required
then
(190-x) = amt of sterling silver
:
A typical mixture equation
.075(190-x) + x = .18(190)
14.25 - .075x + x = 34.2
1x - .075x = 34.2 - 14.25
.925x = 19.25
x = 19.25/.925
x ~ 21.57 grams of pure copper
then
190 - 21.57 = 168.43 grams Br Sterling</PRE>