I'm tutoring a math student and I'm having trouble with this question
Q : A sub-committee of 7 members must be formed from 15 students. There are 9 male students and 6 female students. What is the probability that there are EXACTLY 3 females on the sub committee.
A : The official answer is : 56/143
But according to my calculations :
(6C3 + 9C4) / 15C7 = (20 + 126) / 6435 = 146/6435
I'm not sure where I'm going wrong?