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Home / Assignment Help / The mean life of pairs of shoes is 40 months with a standard deviation of 8 months. if the life of the shoes is normally distributed, how many pairs of shoes out of one million will need replacement before 30 months? round your answer to the nearest integer.

# The mean life of pairs of shoes is 40 months with a standard deviation of 8 months. if the life of the shoes is normally distributed, how many pairs of shoes out of one million will need replacement before 30 months? round your answer to the nearest integer.

You need to determine the number of ways in which 30 competitors from 50 can qualify. First, you have to realize that the order is irrelevant, that is: it is the same competitor_1, competitor _2, competitor _3 than competitor_3, competitor_2, competitor_1, or any combination of those three competitors.

So, the number of ways is which 30 competitors from 50 can qualify is given by the formula of combinations, which is:

C (m,n) = m! / (n! * (m -n)! )

=> C (50,30) = 50! / (30! (50 – 30)! ) = (50!) / [30! (50 – 30)!] = 50! / [30! 20!] =

= 47,129,212,243,960 different ways the qualifiying round of 30 competitors can be selected from the 50 competitors.