by Angela Newing
Five cyclists each have less than 12 helmets, none having two of the same colour and no two cyclists having the same number of helmets. Each wear their helmets in a fixed sequence of different colours on different days until all colours have been used once at which point they repeat their sequence.
On both 1st September and 1st October Alan, Bill, Charles, Dave and Eric wore mauve, red, red, orange and green respectively. On Septemeber 11th there was one mauve, one white, one green and two reds; on the 19th Dave wore orange, Eric wore green and the others wore red; on the 22nd and 23rd Eric wore orange and white respectively.
In the alphabetical order of their names what colour helmets did they wear on 11th of September?