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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
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.
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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.