Problem Solving

Hi,

I never saw this kind of problem in the OG 12th edition, only appeared once in OG quant, please help me understand the steps in solving this problem, thanks! I don't see what kind of principle is being tested here.

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A certain clock marks every hour by striking a number of times equal to the hour, and the time required for a stroke is exactly equal to the time interval betweeen strokes. At 6:00 the time lapse between the beginning of the first stroke and the end of the last stroke is 22 seconds. At 12:00, how many seconds elapse between the beginning of the first stroke and the end of the last stroke?

I posted a solution here:

https://www.beatthegmat.com/question-fro ... 79273.html