Why are multiple RARs bigger in size than their content file

In the past I have found that RARs are the same (or very nearly the same) size as their file.
Ie
175mb file = 100mb + 75mb RARs
350mb file = 3 x 100mb + 50mb RARs
I have checked RAR sizes over the past week, all the combined RAR sizes have been notably bigger than the files inside.
What is going on?
Answer #1
That can’t be correct. Either the Rar would be nearly the same size as the content or less than the content. If you’re checking the file size by going into winrar then try re-installing wirar and make sure you have the latest version. If you’re using right click then properties, then I have no clue what could be wrong.
Answer #2
10% recovery
Answer #3
It is most likely due to whoever created the rars included recovery data so that if one rar becomes corrupt the other rars contain enough data to recover one or more in the archive. Add to that, if they used light compression the archives could be of greater size than the files they contained.
The recovery record increases the size of an archive. The size of the recovery record may be approximately determined by the following formula:
[ARCHIVE size]/256 + [NUMBER of recovery sectors]*512 bytes.
http://win-rar.com/index.php?id=24&kb=1&kb_article_id=149
Answer #4
Ok, thank you.
Answer #5
It also depends on the content of the .rar archive(s).
For example, movies are already in a compressed format, and archiving them will do little to make them smaller.