Answer the questions below. \( \begin{array}{l}\text { (a) A company has } 33 \text { salespeople. A board member at the company asks for a list of the top } 4 \\ \text { salespeople, ranked in order of effectiveness. How many such rankings are possible? } \\ \text { (b) How many different committees of size } 4 \text { can be formed from } 14 \text { people? } \\ \text { (b) }\end{array} \)
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The Deep Dive
To solve these problems, we can use the concept of permutations and combinations. (a) To find the number of possible rankings of the top 4 salespeople from a group of 33, we use permutations since the order in which we rank them matters. The formula for permutations is given by: \[ P(n, r) = \frac{n!}{(n-r)!} \] In this case, \( n = 33 \) and \( r = 4 \): \[ P(33, 4) = \frac{33!}{(33-4)!} = \frac{33!}{29!} = 33 \times 32 \times 31 \times 30 = 1,413,720 \] So, there are 1,413,720 possible rankings. (b) For forming committees, we use combinations because the order of selection does not matter. The formula for combinations is: \[ C(n, r) = \frac{n!}{r!(n-r)!} \] Here, \( n = 14 \) and \( r = 4 \): \[ C(14, 4) = \frac{14!}{4!(14-4)!} = \frac{14!}{4! \times 10!} = \frac{14 \times 13 \times 12 \times 11}{4 \times 3 \times 2 \times 1} = 1001 \] Thus, there are 1,001 different committees of size 4 that can be formed from 14 people.