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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


To get a side length of 12, 

  • the side of length 3 could be enlarged by a scale factor of 4
    or
  • the side of length 4 could be enlarged by a scale factor of 3
    or
  • the side of length 6 could be enlarged by a scale factor of 2


The perimeter of triangle A is 3 + 4 + 6 = 13, so the possible perimeters of triangle B are:

12 + 16 + 24 = 52 (following an enlargement by a scale factor of 4)
or
9 + 12 + 18 = 39 (following an enlargement by a scale factor of 3)
or
and 6 + 8 + 12 = 26 (following an enlargement by a scale factor of 2)


 

You can find more short problems, arranged by curriculum topic, in our short problems collection.