Question

A group contains n persons if the number of ways of selecting 6 persons is equal to the number of ways of selecting 9
persons, then the number of ways of selecting four persons from the group​

Answer 1

Step-by-step explanation:

The number of ways of selecting r person out of n is nCr

As per your question we can write mathematically the given condition in the form of equations as shown below

nC5=nC8

Where n is the number of persons

On solving

n=13

Now the required answer can be found by calculating 13C2

Therefore 13C2=78