Question 1099709
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 If a grandfather clock takes 30 seconds to strike six, how long does it take to strike 12?   THINK! This one is not as easy as it may seem.
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A beatiful Wikipedia article  https://en.wikipedia.org/wiki/Striking_clock  says:


<pre>
    A striking clock (also known as chiming clock) is a clock that sounds the hours audibly on a bell or gong. 
    In 12-hour striking, used most commonly in striking clocks today, the clock strikes once at one a.m., twice at two a.m., 
    continuing in this way up to twelve times at 12 noon, then starts again, striking once at one p.m., 
    twice at two p.m., up to twelve times at 12 midnight.
</pre>

Armed with this knowledge, &nbsp;let me re-solve this problem by another way.


The striking clock, &nbsp;when striking &nbsp;six, &nbsp;has &nbsp;5 &nbsp;(five) &nbsp;time intervals between the strikes. 


It means that each such time interval is &nbsp;&nbsp;{{{30/5}}} = 6 seconds.


12 strikes have &nbsp;11  time intervals between the very first and very last strikes.


Hence, &nbsp;it will take  (6 seconds * 11 intervals) = 66 seconds from the first strike to the last one.



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Dear TUTORS !  &nbsp;&nbsp;It is well known &nbsp;(and one can say even &nbsp;<U>FAMOUS</U> !) &nbsp;<U>entertainment problem for children of the &nbsp;1 - 2 - 3 grade</U> (!!!), 


&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;and each generation re-opens it again and again.



This problem  counts as many years as striking clocks do exist: &nbsp;<U>hundreds years</U>.



And &nbsp;&nbsp;(or &nbsp;BUT) &nbsp;&nbsp;&nbsp;the &nbsp;&nbsp;solution &nbsp;&nbsp;remains &nbsp;&nbsp;the &nbsp;&nbsp;same &nbsp;. &nbsp;. &nbsp;. (as it is written everywhere).