A public health inspector wishes to inspect four restaurants by the end of the week. She has a list consisting of 26 “high- risk" premises, 68 “medium-risk" premises, and 95 "low-risk" premises that require inspections. How many different ways could a selection of the four restaurants be chosen that includes two “high-risk" and two "medium-risk" premises?
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.
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