How smart was Superman?
Some fun Super Feats of his Super Smarts:
In January 1942, Superman is able to converse fluently with a mermaid despite the fact that her tongue is completely foreign to him because his advanced intellect instantly comprehends her strange language. (Superman #14)
In April 1955, Superman is described as having used his photographic memory to memorize all the files of the Daily Planet.
In January 1958, Superman is able to match up a suspect's fingerprints with those on file in Washington, D.C., as the result of having used his super-memory to memorize the entire fingerprint file of the F.B.I.
In June 1958, while relaxing at his Fortress of Solitude, Superman defeats a great robot he has built in a game of super-chess, despite the fact that the robot - which possesses a super-electronic brain - can think and play with the speed of lightning and plans a million moves at once.
A text dated August 1963 notes that Superman possesses the super-intellect of a score of the world's most brilliant minds put together!Source:
http://superman.nu/a/Encyclopaedia/powers.php