Paper 6 May/June 2010 MATHEMATICS (9709/62) A Levels
لطفا برای اطمینان از عملکرد و تجربه بهتر از مرورگرهای مدرن و به روز مانند کروم یا فایرفاکس استفاده کنید.

The random variable $X$ is normally distributed and is such that the mean $\mu $ is three times the standard deviation $\sigma $. It is given that $P(X \lt 25) = 0.648$
a) Find the values of $\mu $ and $\sigma $.
b) Find the probability that, from 6 random values of $X$, exactly 4 are greater than 25.