security camera direct
The Bike Problem - Maths Homework?
I have this question on a piece of maths homework - direct and inverse proportion. I really can't figure out what to do :/ could you help me or at least give me a clue where to start. 
"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 [presumably indirect]) to pose a similar problem in metric units"
It's on the optional part of the homework in case you feel bad about helping me >.<
Hint: Think about the circumference of the circle. Also relate that problem to the revolution of circle, which is 360°.
Good luck!
