How to update my satisfaction and no.of reviews coloumn in my table 1 coloumn

I am totally newbie in the rails and I have searched for my problem to solve it then I found an example from here. Comming to my problem I have two databases they are

one looks like as follows “Names” table       name place satisfactionscore no.   ofratings rank
1          raj usa 2          ravi usa

And I user_ratings table looks like

   id user_id names_id R1 R2 R3 R4 R5
1         1               1       2     3    4
      2         2               1             4             5
      3         3               2        2     3    3       3   3

Now I am trying to find the satisfaction score immediately after updating the values.
and no.of ratings
My formula is for finding is satisfaction score is

  attribute score[ (sum(r1)/no.of rating for r1) + (sum(r2)/no.of rating for r2)+(sum(r3)/no.of rating for r3)+..+(sum(r5)/no.of rating for r5)]

 Where the total no.of ratings is (sum(no.of ratings for r1+ r2+ r3+..+r5))

For satisfaction score (attribute score/ ratings)

So how can I find the statisfaction score.

I have kept in my ratings model as

after_create :  update_post_average_rating
def update_post_average_rating  update_average_rating

and in my names model as

def update_average_rating
update_attributes(:satisfaction => self.ratings.average(:ratings))

  Can any one tell me how to do this. I am unable to understand how can I do it.

First work right through a good tutorial such as
(which is free to use online). That will show you the basics of
rails. Also look at the Rails Guides.