A can do 50% more works as B can do in the same time. B alone can do a place of works in 20 hours. A with the help of B , can finish the same work in how many hours?"
In a class, there are 18 boys who are over 16cm tall. IF these constituted three-fourths of boys and the total number of boys is two thirds of the total number of students in the class, what is the number of girls in the class