Some Helpful Tools
This section will cover the fundamentals of probability.
Probability is not only used to show possible outcomes in many different situations, but also favorable outcomes.
For example, probability can tell you what the odds are for:
3 boys
11 children total
The probability of the class choosing a boy is 3:11 or 27%.
8 chocolate caramel pieces
20 pieces altogether
Notice that one forth of the color wheel is a different color.
Favorable Outcomes
- winning a contest
- the probability of rain or snow
- the view of a public opinion, and so on.
Example 1:
The forecast may predict a 30% chance of snow. Since 30% is not a large number, the chance for snow is not as likely as 70% or 80%.
Probability only shows the strongest possible outcome based on past performance and outcomes available. There are no guarantees as you might have guessed.
The probability of the class choosing a girl is 8:11 or 73%.
8 girls
11 children total
What is the probability of the class choosing a girl?
What is the probability of the class choosing a boy?
Example 3:
Let's say that we have a box of candy that contains 20 pieces of chocolate-
covered candy.
Of the 20 pieces, there are the following:
- 8 chocolate caramel pieces
- 5 chocolate peanut pieces
- 7 chocolate vanilla cream pieces.
What is the probability of choosing a chocolate caramel piece of candy?
Our fraction can be reduced to lowest terms.
2
5
Assume that the spinner can stop on any color. There are four possible outcomes. The probability that the spinner will stop on any of the colors shown on the wheel is 1:4.
A favorable outcome occurs when you spin the spinner and it lands on the color you want.
Look at the formula below to help you figure out the probability.
Probability can be expressed as a ratio, a fraction, and also a percent. Probability ranges in value from 0 to 1.
Probability of Events
For every 5 pieces of candy, 2 of those pieces are likely to be chocolate caramel.
The chance that a chocolate caramel piece will be chosen is 2:5 or 2 to 5.
This means if the probability is 1, there is a 100% chance that some event will occur.
If it is less than 1, the probability will be expressed in the form of a fraction, which is greater than zero but less than 1.
Example 1:
What is the probability of the spinner landing on the color blue?
There is a 0% chance of the spinner landing on yellow since the choices are only red, orange, green, and blue.
Example 2:
What is the probability of the spinner landing on red, orange, green, or blue?
Keep in mind that the greater number of favorable outcomes compared to the total number of outcomes available, the greater chance of choosing a favorable outcome.
Example 2:
A class of 8 girls and 3 boys will take a vote for the next class president. They will do this by putting their names in a hat and drawing the name to see who the new class president will be.
Set up a ratio to find the answer to the questions below.
Math: Probability - Tutorial
