Question

A college has thirteen instructors qualified to teach a special computer laboratory course which requires two instructors to be present. How many different pairs of instructors could there be?

Answer 1

156 different pairs will be there.

Explanation:

As the order is essential as we need different pairs therefore permutations will be used.

A permutation is any ordered subset of the objects r selected with regard to their order, from the set of n distinct objects. It is given by nPr where n> r

Total number is 13 and required number is 2

n= 13 and r= 2

13 P2= 156 possible combinations.

A combination is any subset of the objects r selected without regard to their order, from the set of n distinct objects. It is given by nCr where n> r