Seven Languages In Seven Weeks - Ruby

I've finished the second chapter of Seven Languages in Seven Weeks by Bruce Tang, which is on Ruby.  I already knew a little Ruby, so I was familiar with some of the content.  But the chapter, despite not being that long, covers some more advanced topics that I either didn't know or wasn't that familiar with.  Overall, it's a good start to an interesting book.  Answers to the problems aren't provided, so I've posted my answers on GitHub.  Feel free to review them and notify me of any incorrect answers or improvements to them.

Ruby has foremost been designed to increase the efficiency of the programmer versus making the language itself performant, and this emphasis is clearly evident.  I really appreciate how the language can be so expressive yet concise.  I've enjoyed messing with Ruby and can see why so many developers prefer to work with it.  Without knowing much about the Ruby environment, I'm wondering why more IT departments aren't adopting Ruby and Rails (or at least not adopting it faster than the current rate).  It seems like a great platform for rapidly implementing an application.  I know Ruby gets knocked for its performance, but in my experience there's a greater concern for implementing and releasing functionality in a timely manner than there is for ensuring a certain level of performance for the application.  It's a paradigm shift for many IT departments, but one that seems to offer large dividends.

I was interested in learning Ruby before reading this chapter, and now I'm even more interested.  But for now, it's on to Io...