RUE
regret
MIRROR is a six letter word with three r's in it
The three-letter word for scull is "oar."
ore
rat
E A R
air
mar
tar
A three-letter word that means "exist" is almost always "are." See if it will work.
Mirror has three rs and its a 6 letter word. so it has the most percentage of R's. Is that what you mean?
Car Bar Tar