Ex 6.4, 9 - Chapter 6 Class 11 Permutations and Combinations

Transcript

Ex 6.4, 9 In how many ways can a student choose a programme of 5 courses if 9 courses are available and 2 specific courses are compulsory for every student? Hence, the student has to select 3 courses out of remaining 7 courses Here, n = 7 & r = 3 No of ways selecting 3 course out of 7 course = nCr = 7C3 = 7!/(3!(7 3)!) = 7!/(3!(7 3)!) = 7!/3!4! = (7 6 5 4!)/(3 2 1 4!) = (7 6 5 )/(3 2 1) = 35 ways