Factorial Expressions and Probability
(1) You can answer any 15 questions from the 18 questions on an exam. In how many different ways can you choose the questions, assuming that the order in which you choose the questions is irrelevant?
(2) 7!11!/4!13! Find the Value
(3) Suppose that the time required to complete a 1040R tax form is normally distributed with a mean of 90 minutes and a standard deviation of 10 minutes. What proportion of 1040R tax forms will be completed in less than 100 minutes? Round your answer to at least four decimal places.