Combining probabilities

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.


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?