how to filter this array?

[simpleton]

I have an array called headlines with lots of strings in it. Each string has a #rhyme_keys methods available on it which essentially gives it one of let's say 100 types.
I want to remove all strings from the array who's #rhyme_key type is unique to the array (i.e. if 2 or more strings both have the same of any of the 100 types, they can stay).

I've tried starting off here:

#store all possible types in a new array
rhyme_keys_array = [] << headlines.map{|i| i.rhyme_keys }

#convert it to a hash so that the 100 types are mapped as keys, and their frequency is mapped as values
rhyme_keys_array.flatten.inject(Hash.new(0)){|i,c| i[c]+=1; i}

#Now I don't know how to check against this new hash. Theoretically I think it's like the idea below, but I don't know how to express it syntactically:

hrk = headlines.map{|i| i.rhyme_keys }
if hrk.count < 2 (in the value of the corresponding rhyme_key in the hash) then remove i from headlines.

Does this make sense?