The masses of metal components, M M\,M grams, are normally distributed with a standard deviation of 3.2. Given that P(M<12)=0.42P(M < 12) = 0.42P(M<12)=0.42, calculate the mean mass of the components.
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.