Virginia SOL Math / Grade 5 / Probability & Statistics

5.PS.3

Probability and the Counting Principle

What you'll learn

  • List the sample space for a simple experiment
  • Use the counting principle to count outcomes
  • Determine the probability of an outcome

Words to know

Outcome —
a possible result of an experiment
Sample space —
the set of all possible outcomes
Probability —
how likely an outcome is, from 0 to 1
Event —
one or more outcomes we are interested in
Counting principle —
multiply choices to count total outcomes

Why it matters Probability helps us judge how likely something is, from a coin toss to the weather, so we can make smart predictions.

Worked examples

Model ItI do

A bag has 2 red and 3 blue marbles. Find the probability of drawing red.

There are 2 red marbles out of 5 marbles total. The probability of drawing red is 2 out of 5, written 2/5.

Try It TogetherWe do

You have 3 shirts and 2 pairs of pants. How many outfits are possible?

Use the counting principle and multiply the choices: 3 x 2 = 6. There are 6 possible outfits.

Now YouYou do

A spinner has 4 equal sections numbered 1 to 4. Find the probability of landing on 3.

Count the favorable outcomes over the total outcomes. Check your answer in the back of this chapter.

Practice

Mastered 0 of 11

Warm-up

Ease in with the basics.

  1. 1.A number cube is rolled. What is the probability of rolling a 2?

  2. 2.A bag has 2 red and 2 blue marbles. What is the probability of drawing red?

  3. 3.You have 3 shirts and 3 hats. How many outfits are possible?

On Level

The core Quick Check from the book.

  1. 1.A coin is flipped. What is the probability of heads?

  2. 2.A bag has 1 green and 3 yellow marbles. What is the probability of green?

  3. 3.You have 2 hats and 4 scarves. How many combinations are possible?

  4. 4.A number cube is rolled. What is the probability of rolling a 6?

  5. 5.How many outcomes are in the sample space of tossing one coin?

Challenge

Stretch your thinking.

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

  2. 2.A meal has 4 main dishes, 3 sides, and 2 drinks. How many different meals are possible?

  3. 3.A spinner has 8 equal sections numbered 1 to 8. What is the probability of landing on an even number?