A grandfather clock takes 30 seconds to strike 6:00. The timing starts right at the first bong and ends right at the 6th. And we assume that the bongs themselves take 0 seconds.
How long does the clock take to strike 12:00? For any given hour of the day, how long does it take to strike that hour?
Solution
With the assumption that the bongs themselves are instantaneous, there are 6 seconds between bongs because at 6:00 there are 5 inter-bong intervals. For 12:00 there are eleven of these 6-second intervals, so the total is 66 seconds. For o-clock it takes the clock seconds to do its bonging.