From: Puzzles And Brain Teasers
Drawing from OO.com.au...
A grandfather clock chimes the appropriate number of
times to indicate the hour, as well as chiming once at
each quarter hour. If you were in another room and
heard the clock chime just once, what would be the
longest period of time you would have to wait in order
to be certain of the correct time?
You would have to
wait 90 minutes between 12:15 and 1:45.