# Probability

### The chance that something will happen

## How the lesson is taught.

**1.** Begin the lesson by asking students to define probability (the likelihood or chance that a given event will occur). Probability is usually expressed as a ratio of the number of likely outcomes compared with the total number of outcomes possible. Ask students if they can give an example of probability.

**2.** To help students understand probability, work on the following problem as a class: Imagine that you have boarded an airplane. The rows are numbered from 1 to 30, and there are six seats per row, three on each side of the isle. Seats in each row are labeled A through F. Using that information, work together as a class to solve the problems listed below.

- How many seats are in the airplane?
*180 seats* - What are your chances of sitting in row number 7?
*6/180, or 1/30* - What are your chances of sitting in a window seat?
*There are two window seats per aisle, for a total of 60 window seats. Your chances of seating at a window would be 60/180, or 1/3.* - What are your chances of sitting in an "A" seat?
*There are 30 A seats, so your chances are 30/180, or 1/6.* - What are your chances of sitting in an even-numbered row?
*Of the 30 rows, 15 are even-numbered, so your chances are 15/30, or 1/2.*

**3.** To figure out each problem, students must set up a ratio between the total number of outcomes—in these problems either the total number of seats or rows—and the specific question asked.