Homework Help: Math Concentration

Posted by missy on Sunday, June 26, 2011 at 10:21pm.

Joe has a ring weighing 10 grams made of an alloy of 13% silver and the rest gold. He decides to melt down the rings and add enough silver to reduce the gold content to 69%. How many grams of silver should he add?

My set up is:

10 (.13 + .87) = 10 (.13 + X + .69)

I'm not sure if that's correct.

Math Concentration - Henry, Tuesday, June 28, 2011 at 5:18pm
Silver = 0.13 * 10 = 1.3 grams.

Gold = 10 1.3 = 8.7 grams.

New Alloy: Gold=69% of total solution.

G / (G+S) = 0.69,
8.7 / (8.7 + S) = 0.69,
Cross multiply:
6 + 0.69S = 8.7,
0.69S = 8.7 - 6 = 2.7,
S = 3.91 Grams of silver, total.
3.91 - 1.3 = 2.6 grams of silver added.

Answer this Question

Related Questions

Physics(class) /Math (problem) - Joe has a ring weighing 16 grams made of an ...
algebra - Joe has a ring weighing 15 grams made of an alloy of 20 silver and the...
Chemistry - A piece of metal alloy (a solution of metals) is made of gold and ...
algebra - assume that a jeweler needs 80 grams of an alloy that is 30% gold. He ...
College Algebra - Chemistry - A goldsmith has two gold alloys. The first alloy ...
Chemistry - A homogenous mixture of metals is called an alloy. An alloy is found...
algebra - a jeweler purchased 5 oz of a gold alloy and 20 oz of a silver alloy ...
Chemistry - To assay silver content in an alloy, a 13.38 g sample of alloy was ...
Physics - Archimedes purportedly used his principle to verify that the king'...
chemistry - Archimedes used density along with mass and volume of alloys (...

For Further Reading

First Name:
School Subject:
Answer: