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Home » Find the number of ways in which a committee of 2 teachers and 3 students can be formed out of 10 teachers and 20 students. In how many of these committees (i)a particular teacher is included? (ii)a particular student is included? (iii)a particular student is excluded?
Find the number of ways in which a committee of 2 teachers and 3 students can be formed out of 10 teachers and 20 students. In how many of these committees
(i)a particular teacher is included?
(ii)a particular student is included?
(iii)a particular student is excluded?
Rs aggarwal Maths CBSE Class 11 Chapter 9 Exercise 9B
Find the number of ways in which a committee of 2 teachers and 3 students can be formed out of 10 teachers and 20 students. In how many of these committees
(i)a particular teacher is included?
(ii)a particular student is included?
(iii)a particular student is excluded?

Answer : Since a committee is to be formed of 2 teachers and 3 students

  • When a particular teacher is included

No. of ways in which committee can be formed = 9C1    20C3

= 9720 ways

  • A particular student is included

Since a particular student is always selected so ways of selecting 2 teachers and 2 students from 10 and 19 respect. is = 10C2     19C2 ways

= 7695 ways

  • A particular student is excluded

Since 1 particular student is excluded so, ways of selecting 2 teachers and 3 students from 10 and 19 respt. is = 10C2               19C3 ways

= 43605 ways

 

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