An alloy of tin and copper consists of 15 parts of tin and 105 parts of copper. Find the percentage of copper in the alloy?

Explanation

To find the percentage of copper in the alloy, we can follow these steps:

### Step 1: Find the total number of parts in the alloy.
The alloy consists of 15 parts of tin and 105 parts of copper.

\[ \text{Total parts} = \text{Parts of tin} + \text{Parts of copper} = 15 + 105 = 120 \]
...