Question

In how many ways can student choose 5 courses out of 9 courses if 2 courses are compulsory for every student ?

Answer 1

Out of 9 courses 2 are compulsory. So students can choose from 7 courses only. Also out of 5 courses that students need to choose, 2 are compulsory.

So they have to choose 3 courses out of 7 courses. This can be done ${}^7{C}_3=35$ ways.