6. The time taken, in minutes, by children to complete a mathematical puzzle is assumed to be normally distributed with mean \(\mu\) and standard deviation \(\sigma\). The puzzle can be completed in less than 24 minutes by \(80 \%\) of the children. For \(5 \%\) of the children it takes more than 28 minutes to complete the puzzle.
- Show this information on the Normal curve below.
- Write down the percentage of children who take between 24 minutes and 28 minutes to complete the puzzle.
- Find two equations in \(\mu\) and \(\sigma\).
- Hence find, to 3 significant figures, the value of \(\mu\) and the value of \(\sigma\).
A child is selected at random.
- Find the probability that the child takes less than 12 minutes to complete the puzzle.
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