# NCERT Class 11 Mathematics Solutions: Chapter 7 – Permutation and Combinations Miscellaneous Exercise Part 4 (For CBSE, ICSE, IAS, NET, NRA 2022)

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1. From a class of students, are to be chosen for an excursion party. There are students who decide that either all of them will join or none of them will join. In how many ways can the excursion party be chosen?

From the class of students, are to be chosen for an excursion party.

Since there are students who decide that either all of them will join or none of them will join, there are two cases.

Case I: All the three students join.

So, the remaining students can be chosen from the remaining students in ways.

Case II: None of the three students join.

So, students can be chosen from the remaining students in ways.

So, required number of ways of choosing the excursion party is

2. In how many ways can the letters of the word be arranged so that all the S՚s are together?