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.
Practise Edexcel A Level Maths The Normal Distribution with exam-style questions for A Level Maths. 439 questions, matched to the Edexcel A Level Maths (9MA0) specification and written in Paper 1, Paper 2 and Paper 3 style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.
