The coke machine in college takes 50 pence pieces. It also takes a certain foreign coin of traditional design...
A white cross is placed symmetrically in a red disc with the central square of side length sqrt 2 and the arms of the cross of length 1 unit. What is the area of the disc still showing?
A security camera, taking pictures each half a second, films a
cyclist going by. In the film, the cyclist appears to go forward
while the wheels appear to go backwards. Why?
In that problem I'd been finding designs for streamers - this problem follows on from that.
Can you find a design with only one centre of rotation?
I noticed that if there are mirror lines across the strip, and if there is also a horizontal mirror line, then the strip always seems to have rotation symmetry.
Can that be explained?