Ruby on Rails Error

I’ve been working on this for a long time.  I get this error when trying to work a sql statement like so:

@names = CommonGivenName.find(:all, :conditions => [ “common_given_names.name LIKE                                   #{params[:descendant][:given_name]}%’”])

I keep getting this error:  malformed format string.  I couldn’t figure out the problem, but apparently, Rails doesn’t like the % sign.  After adding a second one, the query ran just fine.  If anyone has any ideas on this, I’d be interested in learning.  I just know it works this way.