Question

combinations and permutations:there are 13 people in an office with 5 different phone lines . if all the lines begin to ring at once ,how many groups of 5 people can answer these lines?

Answer 1

The number of people in the office is 13. We want to select different groups of 5 people

Number of ways that the first phone can be answered = 13

Number of ways that the second phone can be answered = 14

Since order is anot allowed, we would apply combination. Thus, the number of ways is

13C5 = 1287