The annual rainfall in a specific region is normally distributed with a mean of 850 mm. Records show that in 20% of years, the rainfall is more than 1000 mm.
Find the standard deviation of the annual rainfall.
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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.