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Speedy Sidney
Two trains set off at the same time from each end of a single straight railway line. A very fast bee starts off in front of the first train and flies continuously back and forth between the two trains. How far does Sidney fly before he is squashed between the two trains?
Rule of Three
If it takes four men one day to build a wall, how long does it take 60,000 men to build a similar wall?
Digital Times
Which segment on a digital clock is lit most each day? Which segment is lit least? Does it make any difference if it is set to 12 hours or 24 hours?
Age 11 to 14 Short
Challenge Level
Answer: $\frac23$
In each minute, the two clocks showed the same time for $40$ seconds, i.e. they showed the same time for ${40\over60} = {2\over3}$ of the day.
This problem is taken from the UKMT Mathematical Challenges.
You can find more short problems, arranged by curriculum topic, in our short problems collection.
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NRICH is part of the family of activities in the Millennium Mathematics Project.
NRICH is part of the family of activities in the Millennium Mathematics Project.