Math Study Guide: Topic 6: Probability and Combinations (pages 34-37)

Question 1

What is the “probability” of an event happening mean?

Answer 1

The “probability” of an event happening is the number of ways it can happen divided by the total number of events that can happen.

Question 2

How would you solve the following?

A jar has 3 blue marbles, 4 green marbles, and 5 red marbles. What is the probability of picking a blue marble?

Answer 2

There are 3 blue marbles, and a total of 3 + 4 + 5= 12 total marbles.

Therefore, the probably of picking a blue marble is 3/12 or ¼

Question 3

How do you solve a probability question when you are asked about two events happening?

Answer 3

Multiply the two individual probabilities.

Question 4

How would you solve the following?

In a jar of 3 blue marbles, 4 green marbles, and 5 red marbles, what is the probability of pulling out two blue marbles?

Answer 4

Once the first blue marble is pulled out, there are only 2 blue marbles left - and only 11 marbles left. So the probability of the second blue marble is 2/11

Multiply the two probabilities:

3/12 x 2/11 = 3/66 = 1/22

Question 5

How would you solve the following?

Jane has 6 different color shirts and 7 different color pants. How many ways can Jane get dressed?

Answer 5

Just multiply:

6 x 7 = 42