The time taken for a pizza delivery is normally distributed with a mean of 28 minutes. It is found that 15% of deliveries take longer than 35 minutes.
Find the standard deviation of the pizza delivery times.
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Markscheme
3.5 Finding the mean and standard deviation Questions
48 exam-style questions on Edexcel A Level Maths 3.5 Finding the mean and standard deviation. Each one has a worked solution and a mark scheme showing where the marks go.