How much copper and how much 10% alloy were used to produce 36kg of the 25% alloy?

Question

Pure copper was mixed with 10% copper alloy to produce 25% copper alloy. How much copper and how much 10% alloy were used to produce 36kg of the 25% alloy?

Answer 1

Hello, thank you for taking the time to post your question!

The key on this type of question is that you want to use the information given in order to form an equation.

On this one that means

x + y = 36     because we know that there are 36 kg total

1.00x + 0.10y = 36(0.25)      because “x” has 100% purity, y has 10% purity, and the end combination has 25% purity and weighs 36 kg

To solve from there then I would substitute in y = 36 – x into the second equation and then solve for the value of “x” algebraically.

When I do that using a calculator I get x = 6 and then y = 30 for the underlying values, meaning that 6 kg of pure copper and 30 kg of the 10% copper alloy were used in order to produce the 36 kg of the 25% alloy

I hope that helps get you moving in the right direction! Feel free to reach out if you have any additional questions beyond that :)

Answer 2

36 kg of Alloy which is 25% copper means 9 kg of copper and 27 kg of other metal.

 

The only place the other metal came from was the original alloy, which is 10% copper and 90% other metal.

90% of the original alloy is 27 or .9A = 27 So A = 30. So i had 30 kg of the original alloy, 3 kg copper and 27 kg other.

 

I need 6 kg of copper then giving me 36 kg all together and 9 kg copper.

 

Original alloy is 3/30 or 10% copper.

New alloy is 9/36 or 25% copper.

 

Sorry, but equations weren't really necessary.