Now that you can draw probability tree diagrams, I now show you how to combine probabilities to evaluate the probabilities of combined outcomes and mutually exclusive events.

## Examples

Two examples for you to try, the first is relatively straight forward but I would certainly encourage you to try the second.

1) In a factory, machines A and B produce electronic components. Machine A produces 40% of the components and machine B produces 60%. Some of the components are defective. Machine A produces 4% and machine B, 3% defective components. Find the probability that a randomly selected component is

(a) produced by machine B and is defective.

(b) defective

2) In a recent survey it was found that in a group of 60 girls and 40 boys, the probability of a person being left handed was 0.18. The probability of a girl being left handed is 0.1. What is the probability of a boy being right handed?