FUN with Girls vs Boys

A boy introduced a girl as the daughter of the son of the mother of his aunt. The girl is boy's:

The average weight of girls is 15 and the average weight of boys is 30 and the average weight of boys and girls both is 25. If the number of boys are 12, then the number of girls is :

The average weight of girls is 15 and the average weight of boys is 30 and the average weight of the boys and the girls both is 25. If the number of boys are 12, then the number of girls is :

Six boys and six girls sit in a row randomly. Find the probability that (i) the six girls sit together,(ii) the boys and girls sit alternately.

A boy and a girl are facing each other. If the boy is standing at the North-West direction of the girl, in which direction is the girl to the boy?

A boy and a girl are playing in a park. The only daughter of the maternal grandfather of the girl, is the sister of the boy's father. How is the boy related to the girl ?

A committee of 4 boys and 3 girls is chosen from 8 boys and 5 girls. One of the boys is a brother of one of the girls. Probability that both are in the committee is