A bag contains $4$ red and $5$ blue counters. Two are selected at random without replacement. A

Question

A bag contains $4$ red and $5$ blue counters. Two are selected at random without replacement. A pupil writes $P(\text{different colours})=\dfrac49\times\dfrac58=\dfrac5{18}$. Explain the error and calculate the correct probability.[3]

Accepted Answer

The blue-then-red path was omitted; correct probability $\dfrac59$.

An omitted ordering

An omitted ordering

Solution:

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