I have had a lot of success in my MAC operating systems with a free program called UNARCHIVER...
It works on many files at a time and does RAR... It even "unarchives" as much as it can if a file is incomplete!
I got it in the Apple APP store for free!!
Hope this helps someone, I saw another thread on unzipping files but nowhere did it say about us "Mac" people and it was a closed thread so I hope you don't mind I started this thread!!
Happy New Year from Texas!! Linda