Ambiguous Times/Historical Note

From ProofWiki
Jump to navigation Jump to search

Historical Note on Ambiguous Times

This problem appears in Henry Ernest Dudeney's posthumous $1932$ collection Puzzles and Curious Problems, so is is presumed it first appeared before that date in one of the journals to which Dudeney contributed.

It is also reported that it was independently invented by Andrei Dmitrievich Sakharov while he was on hunger strike in $1985$:

I spent long hours gazing at the clock hanging on the wall of my room.
At night, the dim hospital illumination made it at times difficult for me to distinguish the hour hand from the minute hand, and I thought up the brainteaser:
An absent minder watch-maker accidentally fastens two hands of equal lengths on a clock with the usual twelve-hour dial.
Because of this, there are moments when the time can be read in either of two ways.
Find all the ambiguous moments.


Sources