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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?

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Back in Time

How many times a day does a 24 hour digital clock look the same when reflected in a horizontal line?

Similar Perimeter

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.