Question

There are 15 boys and 10 girls in your class. A four member committee is to be formed from the students of your class. In how many ways this can be done if the committee consists at least three girls

Answer 1

There are 25 students total. 4 students are taken at a time. Then no. Of ways 25!/(25-4)!4!=7286400 ways.

Answer 2

There will be two cases.
In first 3 girls and 1 boy, number of ways = 10C3× 15C1 = 1800 ways
In second case, 4 girls  and 0 boys,
number of ways = 10C4 =210
so total number of possible ways = 1800 + 210 = 2010