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A Problem of Time
Consider a watch face which has identical hands and identical marks for the hours. It is opposite to a mirror. When is the time as read direct and in the mirror exactly the same between 6 and 7?
Back in Time
How many times a day does a 24 hour digital clock look the same when reflected in a horizontal line?
Age 14 to 16 Short
Challenge Level
The lengths of the sides of a triangle A are 3, 4, and 6.
Triangle B is similar to triangle A. One of the sides of triangle B has length 12.
What are the possible perimeters that triangle B could have?
This problem is taken from the World Mathematics Championships
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.