Posted by **victor** on Saturday, November 5, 2011 at 7:23pm.

According to a bank, the time taken by its customers to use cash dispensing machines is normally distributed with a mean of 18 seconds and a standard deviation of 3 seconds.

I) What is the probability that a customer selected at random takes less than 13 seconds?

II) Find the proportion of customers that take :

a) Between 15 and 21 seconds to use the cash dispensers?

b) Between 12 and 24 seconds to use the cash dispensers?

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