AI generatedProbabilityKey Stage 3

Recognising equally likely outcomes

Recognising equally likely outcomes.

  • Probability = favourable outcomes ÷ all outcomes when individual outcomes are equally likely.
  • A probability lies between 0 and 1; complementary probabilities sum to 1.
  • Experimental relative frequency estimates probability and can vary between samples.

Example 1

A fair pointer spins on this spinner. Are A, B, C and D equally likely? Explain.

Pie chartA90°B90°C90°D90°
Yes.

Equal sectors have equal chances for a fair spinner.

Example 2

A fair pointer spins on this spinner. Are A, B, C and D equally likely? Explain.

Pie chartA60°B120°C90°D90°
No. B is twice as likely as A.

Compare sector angles: B is 120° and A is 60°. Four labels do not imply four equal probabilities.

Your turn

Question 1

A fair pointer spins on this spinner. Are A, B, C and D equally likely? Explain.

Pie chartA90°B90°C90°D90°
Check answer
Yes.

Equal sectors have equal chances for a fair spinner.

Question 2

A fair pointer spins on this spinner. Are A, B, C and D equally likely? Explain.

Pie chartA60°B120°C90°D90°
Check answer
No. B is twice as likely as A.

Compare sector angles: B is 120° and A is 60°. Four labels do not imply four equal probabilities.

Question 3

A fair pointer spins on this spinner. Are A, B, C and D equally likely? Explain.

Pie chartA90°B90°C90°D90°
Check answer
Yes.

Equal sectors have equal chances for a fair spinner.

Question 4

A fair pointer spins on this spinner. Are A, B, C and D equally likely? Explain.

Pie chartA60°B120°C90°D90°
Check answer
No. B is twice as likely as A.

Compare sector angles: B is 120° and A is 60°. Four labels do not imply four equal probabilities.

Question 5

A fair pointer spins on this spinner. Are A, B, C and D equally likely? Explain.

Pie chartA90°B90°C90°D90°
Check answer
Yes.

Equal sectors have equal chances for a fair spinner.

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