Number of black balls = 5
Number of black balls to be selected = 2
Number of selections = ...(i)
Number of red balls = 6
Number of red balls to be selected = 3
Number of selections =
Hence, from (i) and (ii), by fundamental principle of counting, the required number of selections
= 10 x 20 = 200.
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?
A committee of 7 has to be formed from 9 boys and 4 girls. In how many ways can this be done, when the committee consists of :
(i) exactly 3 girls? (ii) at least three girls? (iii) at most 3 girls?