SOLUTION: Brass is an alloy containing only copper and zinc. A particular batch of brass is analysed and found to contain 35g of copper and 15g of zinc. How much zinc would need to be added

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Question 588213: Brass is an alloy containing only copper and zinc. A particular batch of brass is analysed and found to contain 35g of copper and 15g of zinc. How much zinc would need to be added so that the mass of zinc in the brass is 40% of the total mass of the solid? (Show an algebraic solution for the problem)

thanks! :)
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
Brass is an alloy containing only copper and zinc.
A particular batch of brass is analyzed and found to contain 35g of copper and 15g of zinc.
How much zinc would need to be added so that the mass of zinc in the brass is 40% of the total mass of the solid?
:
15 + 35 = 50 mg of alloy to start with
then
15%2F50 = .30 decimal value of of zinc to start with
:
Let x = amt of zinc to be added to make the total 40% zinc
;
Write an amt of zinc equation
.30(50) + x = .40(x+50)
15 + x = .40x + 20
x - .4x = 20 = 15
.6x = 5
x = 5%2F.6
:
x = 81%2F3 grams of zinc required
;
:
Check this, find the amt of zinc now.
.4(58.33) = 23.33
which is 15 g original zinc, plus 8.333 that we added.