Question 1172674
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In your post,  the densities of the ingredient metals are missed.



Brass itself is not an element - it is an alloy, instead, consisting of different components in different proportions, 


so, without a further deciphering/specifications, there is no sense to talk about its density --- it may vary.



THEREFORE, as the problem is posed in the post, it makes a few sense (if any).



To learn more about the term "brass",  input it into the GOOGLE search engine --- and enjoy (!)