<PRE><B>Question 873199</B>
One alloy contains 80% gold and another alloy contains 55% gold. The two alloys are combined to make 40 grams of an alloy that is 70% gold. How many grams of the 80% alloy are used?
Answer 
let x grams alloys contain 80% gold  and y gram alloys  contain 55% gold 
as per conditions given X + Y =40 (1)
80%X +55%Y =70% of 40
.8x +.55 y = 28 
80x +55y =2800 (2) by multiplying (1) by  80 and subtracting  from (2)
80x +80Y =3200
-25y =-400
Y= 16 grams 
X + Y =40
X + 16 =40
X= 24 grams 
Answer  
80%  alloy  contain gold =24 grams 
55% alloy contain  gold =16 grams </PRE>