14A - Addition and multiplication principles

Learning intentions:

In this section we will examine:

    • The addition rule for counting
    • The multiplication rule for counting

The addition rule

When we can identify two, or more, mutually exclusive events (there are no common outcomes) we can use the addition rule of counting. In general, the total number of outcomes of two, or more, mutually exclusive events is found by the sum all available alternatives.

14A - VIDEO EXAMPLE 1:

Will is travelling to Melbourne University. Will can travel by Train or by Bus. The PTV app states there are 3 busses and 4 trains travelling to Melbourne University. How many choices does Will have when travelling to University?

In probability the use of "or" usually requires us to "ADD".

In probability the use of "and" usually requires us to "MULTIPLY".

The multiplication rule

When we can identify two, or more, independent events (one outcome does not affect the other) that are performed successively we can use the multiplication rule of counting. In general, the total number of outcomes when successive events are performed is found by the product of the number of options at each successive stage.

14A - VIDEO EXAMPLE 2:

The Audi R8 comes in two models (V10 and V10 Plus). In both models there are 9 different paint finishes, 7 different rims and 2 types of headlights. How many different configurations are available?

Success criteria:

You will be successful if you can:

    1. Determine when to use the addition or multiplication rule.
    2. Apply the addition and multiplication rules to counting problems.