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Lesson · Grade 5 · Mathematics

Probability as a Fraction

  • Grade 5
  • Mathematics
  • 1 min 17 s
  • British Columbia
  • BC5-MA-36

A bag of 3 red and 2 blue counters shows how to count all the possible outcomes and the outcomes we want, so the probability of picking red is 3/5. The same rule then gives 1/6 for rolling a 4 on a fair die and 1/4 for landing on green on a spinner with 4 equal parts.

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In one sentence

The question this lesson answers

A bag holds 5 counters: 3 red and 2 blue.

If we pick one counter without looking, how likely is it to be red?

Transcript

What the lesson says

A bag holds 5 counters: 3 red and 2 blue.

If we pick one counter without looking, how likely is it to be red?

Each counter is equally likely to be picked.

There are 5 counters, so there are 5 possible outcomes.

3 of them are red, and those are the outcomes we want.

Check: 3 red and 2 blue make 5 counters.

So the probability of picking red is 3 out of 5, or three fifths.

The top number counts the outcomes we want.

The bottom number counts all the possible outcomes.

A fair die has 6 faces, and only 1 of them is a 4.

So the probability of rolling a 4 is 1 out of 6.

This spinner has 4 equal parts, and 1 of them is green.

So the probability of landing on green is 1 out of 4.

When all outcomes are equally likely, probability is the outcomes we want over all the possible outcomes.

Curriculum

Where this fits

British Columbia, Grade 5

Mathematics, Data and probability: probability experiments, single events or outcomesBC5-MA-36

Previous: Double bar graphs with a scaleNext: Experimental and Theoretical Probability: Flip a Coin, Roll a Die

The outcomes and strands follow the British Columbia curriculum.

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