Paper 6 October/November 2009 MATHEMATICS (9709/61) A Levels
لطفا برای اطمینان از عملکرد و تجربه بهتر از مرورگرهای مدرن و به روز مانند کروم یا فایرفاکس استفاده کنید.

The times spent by people visiting a certain dentist are independent and normally distributed with a mean of 8.2 minutes. 79% of people who visit this dentist have visits lasting less than 10 minutes.
a) Find the standard deviation of the times spent by people visiting this dentist.
b) Find the probability that the time spent visiting this dentist by a randomly chosen person deviates from the mean by more than 1 minute.
c) Find the…