The average number of miles (in thousands) that a car's tire will function before needing replacement is 72 and the standard deviation is 18. Suppose that 50 randomly selected tires are tested. Round all answers to 4 decimal places where possible and assume a normal distribution. a. What is the distribution of X? X - N(( 72 18 b. What is the distribution of ? a - N( c. If a randomly selected individual tire is tested, find the probability that the number of miles (in thousands) before it will need replacement is between 73.9 and 76.9. d. For the 50 tires tested, find the probability that the average miles (in thousands) before need of replacement is between 73.9 and 76.9.
Permutations and Combinations
If there are 5 dishes, they can be relished in any order at a time. In permutation, it should be in a particular order. In combination, the order does not matter. Take 3 letters a, b, and c. The possible ways of pairing any two letters are ab, bc, ac, ba, cb and ca. It is in a particular order. So, this can be called the permutation of a, b, and c. But if the order does not matter then ab is the same as ba. Similarly, bc is the same as cb and ac is the same as ca. Here the list has ab, bc, and ac alone. This can be called the combination of a, b, and c.
Counting Theory
The fundamental counting principle is a rule that is used to count the total number of possible outcomes in a given situation.
Only parts b, c, and d


b. From the given information,
c. The required probability will be given by as follows:
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