Now we read our diagram from left to write and do two things:
- Follow each path and write down the outcomes.
- Follow each path and multiply the probabilities.
Along the top path, we encounter heads and then heads again, or HH. We also multiply:
50% x 50% = (.50)x(.50)=.25=25%.
This means that the probability of tossing two heads is 25%.
We could then use the diagram to answer any question about probabilities involving two coins. As an example, what is the probability that we get a head and a tail? Since we were not given an order, either HT or TH are possible outcomes, with a total probability of 25%+25%=50%.