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'A Problem of Time' printed from https://nrich.maths.org/
Tim sent us his excellent answer to this
problem:
The time is approximately 27 minutes 42 seconds past 6
o'clock.
At six o'clock the minute hand and the hour hand are exactly 180
degrees apart. Let the hour hand move through x degrees. Then, if
the time is reversible in a mirror, the minute hand has moved
through (180 - x) degrees. The hour hand moves at 30 degrees per
hour. The minute hand moves at 360 degrees per hour. The time
elapsed during which both hands move is identical. It follows
that
$\frac{(180 - x)}{360} = \frac{x}{30}$
x = $\frac{180}{13}$
Hence, this angle represents $\frac{180}{13}$ x $\frac{1}{360}$ x
60 minutes on the clock face. This reduces to 2$\frac{4}{13}$
minutes (approx. 2 minutes and 18 seconds). Therefore the time is
30 - 2$\frac{4}{13}$ minutes past 6 o'clock; i.e. 27$\frac{9}{13}$
minutes past 6 o'clock.
Laura (West Flegg Middle School, Great
Yarmouth, Norfolk) came very close to this answer. Her solution was
28 minutes past 6 o'clock.