2 The length of aluminium baking foil on a roll may be modelled by a normal distribution with mean 91 metres and standard deviation 0.8 metres.
- Determine the probability that the length of foil on a particular roll is:
- less than 90 metres;
- not exactly 90 metres;
- between 91 metres and 92.5 metres.
- The length of cling film on a roll may also be modelled by a normal distribution but with mean 153 metres and standard deviation \(\sigma\) metres.
It is required that \(1 \%\) of rolls of cling film should have a length less than 150 metres.
Find the value of \(\sigma\) that is needed to satisfy this requirement.
[0pt]
[4 marks]
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