1. How are the probabilities of each set of branches of a tree diagram calculated?

The fact that they must add up to one is very helpful.

2. What sort of problems can be solved using a tree diagram?

Problems where more than one trial are carried out.

e.g. Tossing a coin three times, drawing two coloured balls from a bag of balls.

2. Having drawn the tree diagram, how is the probability of an event calculated?

To calculate the probability of a particular event the probability of the consecutive branches are multiplied together.