Question

[15 Points, Just check for equation]

Sterling silver is an alloy of 92.5% silver and 7.5% copper by weight. You have 15 ounces of 800 grade silver which is 80% silver and 20% copper. How much pure silver should you add to the 800 grade to make sterling silver?

Is the equation for copper 0.075(15 + s) = 3 + s?​

Answer 1

No; 0.075(15 + s) = 3; s = 25 oz

Explanation:

No, but you are close.

The mass of copper in your 800 grade silver is

Mass = 0.20 × 15 = 3 oz

You are adding s oz of silver so that 7.5 % of the total mass is still 3 oz of copper.

The equation becomes

0.075(15 + s) = 3 Divide both sides by 0.075

15 + s = 40 Subtract 15 from each side

s = 25 oz

You add 25 oz of silver to your 800 grade alloy to get sterling .

Check:

0.075(15 + 25) = 3

0.075 × 40 = 3

3 = 3