i installed ruby 1.9.2 with RVM, but when i type “ruby -v” is telling me the ruby v i have is 1.8.7 (mac)

when i write in the treminal "rvm list" i get this:

rvm rubies

   ruby-1.9.1-p378 [ x86_64 ]
   ruby-1.9.2-p136 [ x86_64 ]

but when i type "ruby -v" i get this:

ruby 1.8.7 (2009-06-12 patchlevel 174) [universal-darwin10.0]

what shoud i do?