This is a really tricky probability problem. I have had many 'arguments' over the fact that the probability of drawing a white counter IS NOT 1/2! Set the Number of Trails slider to a value from 100 to 1000. Click on the green flag. The number of times a white counter was drawn and the number of times a black counter was drawn is accumulated and displayed. Running this project at high 'Number of Trials levels' should help you form an intuitive conjecture of the value of the theoretical probability.
This is the fifth of seventy-two problems Lewis Carroll published in his book titled 'Pillow Problems thought out during Wakeful Hours'. For myself, the delightful task of writing a computer algorithm to simulate the action of adding to and taking away white and black counters solidified the theoretical (paper and pencil) solution that is validated in this Monte Carlo simulation. The algorithm doesn't animate anything on the screen so it computes 1000 trails quickly. This is a good exercise for learning how to use lists. I've kept the coding as close to the actual manipulation of a bag and counters as I knew how.
