Rails - Jan 2014 - 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<http://stackoverflow.com/questions/12092964/update-post-attribute-when-new-rating-is-created>.
Comming to my problem I have two databases they are 

one looks like as follows "Names" table

 s.no       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/ total.no.of 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
    self.name.update_average_rating
  end

and in my names model as

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


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

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