Question

An alloy is a mixture of metals. Suppose that a certain alloy is made by mixing 100 grams of an alloy containing 35% copper with 60 grams of an alloy containing 55% copper.

Answer the questions below. Do not do any rounding.
(a) How many grams of copper are in the resulting mixture?
(b) What percentage of the resulting mixture is copper?

Answer 1

(a) 68 grams

(b) 42.5%

Explanation:

You mix 100 g of 35% copper with 60 g of 55% copper to form an alloy. You want to know the number of grams and the percentage of copper in the mixture.

Copper

The total amount of copper is ...

0.35·(100 g) +0.55·(60 g) = 35 g + 33 g = 68 g

There are 68 grams of copper in the resulting mixture.

Percentage

The percentage of copper in the mixture is ...

(68 g)/(100 g + 60 g) × 100% = 68/160 × 100% = 42.5%

The resulting mixture is 42.5% copper.