(Q). In how many ways 5 numbers can be selected from {1, 2, 3, 4, 5, 6, ………. n} such that not all the five numbers are consecutive?
Solution:-
Required number of ways
= number of ways of selecting 5 out of n students – number of ways of selecting 5 consecutive out of n students.
= ⁿC₅ – (n-4)
= ⁿC₅ -n + 4 Answer
