I was Googling for something entirely different and came across a puzzle / illusion, after an hour of not being able to find the answer and having used half a rainforest to aimlessly doodle numbers etc. I resorted to looking at the answers page. Blow me down with a feather a schoolboy answered it!! I am sure therefore that this is no tester for you geniuses out there but I guess I should throw down the gaunlet for the quickest answer
A security camera, which takes one picture each half a second, films a cyclist going by at 8.5 miles per hour on a bike which has wheels of diameter 24 inches. There is a reflector fixed to the spokes of each wheel of the bike. Explain why it is that, in the film, the cyclist appears to go forward while the wheels appear to go backwards. If the cyclist goes a little faster the wheels appear to be stationary. At what speed does this happen?
You will need to know that 1 mile = 1760 yards, 1 yard = 3 feet and 1 foot = 12 inches to do this question.
Can you also change the numbers (not necessarily by direct conversion) to pose a similar problem in metric units?
The stop clock has started at 16:41 GMT
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