Mathematics
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50 mins
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Expressing Probability as Fraction, Decimal and Percentage

Learn to express probability in three ways: as a fraction, decimal and percentage. Use spinners to find the chance of each outcome, then write it in all three forms.

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    Worked example

    1 - Getting Started ~4 mins

    Illustration for Getting Started

    Key point

    Picture a spinner split into four equal colours: red, blue, green and yellow. If we give it a spin, what is the chance it lands on red? See how many different ways you could write that answer down.

    👇 Mark your steps as done as you complete them.

    +5 XP

    2 - Watch and Notice ~9 mins

    Watch three spinners on the board. On each one we work out the chance of a colour by counting the favourable segments (the ones we are asking about — here, the red ones) over the total segments. Then we write that same chance three ways: as a fraction, as a decimal, and as a percentage.

    To turn a fraction into a decimal we divide the top number by the bottom number, then multiply by 100 to get the percentage:

    • 1 ÷ 4 = 0.25
    • 0.25 × 100 = 25%

    So 1/4 = 0.25 = 25%. Look for how a fair spinner shares its chance equally, and be ready to say the third form for the last one before it appears.

    👇 Mark your steps as done as you complete them.

    +10 XP

    3 - Write Each Chance Three Ways in Your Copy ~3 mins

    COPYBOOK MOMENT

    In your maths copy, for each spinner outcome write the probability three ways in a row: first as a fraction, then its decimal, then its percentage. Work these three:

    • Green on the four-colour spinner
    • An odd number on the six-number spinner
    • A red on the five-colour spinner

    Check each row: the three forms should all match the same amount.

    +10 XP

    4 - Try It Together ~9 mins

    Today we work through a fresh spinner together: an eight-segment spinner where three segments are prizes. We find the chance of a prize, then write it as a fraction, a decimal and a percentage.

    This time the fraction does not land on a tidy landmark, so we divide the top by the bottom on the board, then multiply by 100 for the percentage.

    Key point

    Write the chance of a prize three ways: as a fraction, a decimal and a percentage.

    Keep this reference table beside you as you work:

    • 1/2 = 0.5 = 50%
    • 1/4 = 0.25 = 25%
    • 1/5 = 0.2 = 20%
    • 1/8 = 0.125 = 12.5%

    Then we spin it a few times so you can see the outcomes appear. Some of you will come up to set the spinner and read out the three forms.

    +15 XP

    5 - Class Challenge ~10 mins

    Key point

    Today we work through these spinner problems together, each a step harder than the last. Take your time on the decimal for the last one:

    • A 5-section spinner with 1 blue: chance of blue.
    • A 10-section spinner with 3 red: chance of red.
    • A 4-section spinner with 3 stars: chance of a star.
    • An 8-section spinner with 1 winning slot: chance of a win.

    For each one, set it up on the spinner, then write the chance as a fraction, a decimal and a percentage.

    Find the probability three ways

    +15 XP
    Pupil practice
    Module 9 · Data and Chance Data & Chance
    Lesson 110 · Expressing Probability as Fraction, Decimal and Percentage
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