I am doing this lab report, and I've hit a road block. We have to calculate the percent of copper found in our sample of brass. So here's what I did.

Our sample of brass was measured to be 1.077 grams. After doing all of the other stuff, we found that the concentration of copper in our sample came out to 0.111 M. I then followed the instructions our teacher gave us to find the percent of copper: multiply 0.111 M by 100 then divide that by 63.543 mg/mol of Cu then divide the mg of Cu by the mg of our sample of brass. After all of that, the number came out around 16ish percent, but upon looking up the average amount of copper found in brass I found out that it's suppose to be higher.... much higher. Nearly 50% of brass is suppose to be copper. So is there something I did wrong? Were the calculations wrong? Or am I correct?