“…for I felt suddenly as though I were talking to a child…”  pg. 188

“You’re acting like a little boy,” I broke out impatiently.  “Not only that but you’re rude.  Daisy’s sitting in there all alone.” Pg. 93

In this scene, Nick is giving Gatsby somewhat of a pep talk, trying to give him a little more reason to go back out and talk to Daisy.  One can easily see that Nick uses the word ‘boy’ to describe Gatsby’s actions.  In this particular situation, Nick is almost acting as Gatsby’s father, disciplining his manners while at the same time motivating him to get back on the horse.  It just goes to show that Nick is somewhat more mature than Gatsby, and with age comes maturity.  This puts Gatsby at about the age of 14.  Nick's use of the word 'boy' is fairly significant, and it makes it seem that he feels that he is above Gatsby.