If there are 9 pairs of twins, and a committee will be formed with 3 members. In how many ways this committee formed in a way that no siblings in a group?
Choose the most appropriate option
A) 632  B) 672  C) 756  D) 744  E) 740
Firstly, there are 9 ways to choose 3 groups from the 4 groups. Hence 9C3.   Next, with the 3 groups chosen, there are 2^3 choices of choosing either one of the siblings.   Hence, the total number of ways are 9C3 * (2^3) = 672   672
<result>B</result>
If there are 9 pairs of twins, and a committee will be formed with 3 members. In how many ways this committee formed in a way that no siblings in a group?