Chapter 13.1, Problem 31STP

To determine

To identify number of possible outcomes where A can invite friends to birthday dinner.

Answer to Problem 31STP

6

Explanation of Solution

Given information: Choose two friends from 4 friends.

Explanation-

There are four choices for her pick for the first friend. Once she chooses the first friend, there are three other friends to choose from.

Multiply together

  $4\times 3=12$

However, this double counts the answers because picking friend 1 and friend 2 is the same as picking friend 2 and then friend 1.

Hence to avoid duplicity, we divide by 2.

  $\begin{array}{l}\\ \frac{12}{2}=6\end{array}$

Hence, there are 6 possible ways in which she can invite her friends.