Q.3: 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:
(iii) at most 3 girls?
There are 9 boys and 4 girls. A committee of 7 has to be formed.
(ii) At most 3 girls, there can be 4 cases:
(a) Girls =0, so boys in the committee = 7-0 = 7.
Thus, the required number of ways
(b) Girls =1, so boys in the committee = 7-1=6
Thus, the required number of ways
(c) Girls =2, so boys in the committee = 7-2 = 5.
Thus, the required number of ways
(d) Girls =3, so boys in the committee = 7-3 = 4
Thus, the required number of ways
Hence, in this case, the number of ways = 36+336+756+504=1632