Product Rule

Definition

Product Rule for Ordered Pairs

If there are $m$ choices for the first action and $n$ choices for the second action, the number of possible choices for both actions is $mn$.

General Product Rule

Suppose there are $k$ actions, if there are $n_1$ choices for the 1st action, $n_2$ choices for the 2nd action, and so on through $n_k$ actions for the $k$-th action, the number of possible choices for the $k$ actions is given by the product of the number of choices, which is $n_1{n}_2\dots n_k$,

Ex: Company Retirement Plan

8 different bond funds and 12 different stock funds.

• For your portfolio, you are allowed to pick one bond fund and one stock fund How many possible ways are there to pick a portfolio? $=8\times 12=96$