There are 9 jars each with unique labels.
Someone has come and removed all the labels and mixed them up.
If you put the labels back on the jars (without knowing the contents), what is the expected number of labels which would match the contents?
(In reply to
SOLUTION IS WRONG by James)
The solution doesn't say at least one label will be correct. it says that the expected number of correct labels is one. Sometimes there won't be any correct labels, and sometimes there will be more than one. The average number of correct labels, though, is one.