Frankie has two bags each containing 5 coloured sweets; the first bag contains three red and two green sweets, and the second bag contains two red and three green sweets. She picks a sweet from the first bag at random and puts it in the second bag, then she picks a sweet at random from the six sweets that are now in the second bag, and puts it in the first bag.

What is the probability, after carrying out this process twice (so four sweets have been swapped), that both bags contain only one colour of sweet?

What is the probability of this happening after doing the swapping process three times? Or four? Is there a general rule?