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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.
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Age 11 to 14
ShortChallenge 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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