rails -v keeps saying Rails 3.2.13 after installing 4.2.2

What gives?

I typed this in gem install rails -v 4.2.2

After that, I tried rails -v, and it keeps coming out Rails 3.2.13

Why is this?

My ruby version after ruby -v

ruby 2.2.1p85 (2015-02-26 revision 49769) [x86_64-darwin14]