At exactly 4:00, the minute and
hour hands are 120º apart. The
minute hand travels 360º in 60
minutes, or 6º per minute.
The hour hand travels 360º in
12 hours = 720 minutes, or 1/2 º
per minute. So the minute hand
is catching up to the hour hand
at 5.5º per minute. That works out
to 120 / 5.5 = 21 9/11 minutes, or 21.82 minutes
so Thus they meet at 4:21.82