Math · Stage 5

Write the probability of an equally-likely event as a fraction and predict from it

Count the favourable outcomes over the total equally-likely outcomes, write P(event) as a fraction in its simplest form, and use that fraction to predict results.

✦ Math📘 Stage 5 · S5⏱ ~12 min🧒 Ages 9–10★ Free to start

I can write the probability of an equally-likely event as a fraction and predict from it.

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Kavi Turns Chance into a Fraction 🎲

"Last time I put chance on a 0-to-1 line," hoots Kavi, "now I write it as an exact fraction!" Kavi counts a spinner's equal slices. "P(red) means the chance of red — it's the favourable slices over all the equal slices, then I simplify. And once I know the fraction, I can predict: a spinner that's 1/4 red should give about 5 reds in 20 spins! 🦉"

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What your child will learn

1Write the chance as a fractionWhen every outcome is equally likely, the probability of an event is the favourable outcomes over the total outcomes. This spinner has 6 equal slices and 2 are red, so P(red) = 2/6 — which simplifies to 1/3. Tap slices to shade more and watch the fraction change.

2P(event) = favourable ÷ totalMathematicians write the chance of an event as P(event). For equally-likely outcomes, count the favourable outcomes, divide by the total, and simplify. Every probability lands between 0 (impossible) and 1 (certain).

3Use the fraction to predict

4Roll a lot — counts match the fractionEach face of a fair die has probability 1/6. Kavi rolled the die 60 times and tallied the faces. Because 1/6 of 60 = 10, every face was predicted to come up about 10 times. Compare the bars with that prediction.

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A peek inside

A spinner has 5 equal parts: 2 red and 3 blue. Write P(red) as a fraction.

favourable = 2 red parts, total = 5 equal parts → 2 over 5

Try this at home: A bag has 3 red and 4 blue counters (7 in all). Write the probability of red as a fraction. __

Ready to play and learn?

Start the free interactive lesson, or print the handout for screen-free play.

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Part of Math · Stage 5 · S5 on KAVI Academy — a secular, whole-child learning platform for ages 5–12.