How much of an alloy that is 20% copper should be mixed with 500 ounces of an alloy that is 60% copper in order to get an alloy that is 30% ?copper?

Question

How much of an alloy that is 20% copper should be mixed with 500 ounces of an alloy that is 60% copper in order to get an alloy that is 30% ?copper?

Answer 1

HI Kara, the best way to solve this type of problem is to create a table. 

 

Let x represent the amount of 20% cooper allow that is needed.

 

Table:

 

Percent    Amount     Decimal         Total

--------------------------------------------------------

20%            x             .2               .2x

 

60%         500            .6               .6 * 500

 

30%        500 + x       .3               .3 * (500 + x)

 

Equation:

 

.2x + .6 * 500  = .3 * (500 + x)

 

.2x + 300         = 150 + .3x

 

Subtract 150 from both sides:

 

.2x + 150 = .3x

 

Subtract .2x from both sides:

 

.1 * x = 150

 

Divide both sides by .1:

 

x = 1500

 

You will need 1500 ounces of 20% copper to make the 30% copper alloy.

 

Questions?