In a class, there are 18 boys who are over 160 cm tall. If these constitute three-fourths of the 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 ?

A father is now three times as old as his son. Five years back, he was four times as old as his son. The age of the son (in years) is

A waiter's salary consists of his salary and tips. During one week his tips were 5/4 of his salary. What fraction of his income came from tips ?

If you write down all the numbers from 1 to 100, then how many times do you write 3 ?

If 100 cats kill 100 mice in 100 days, then 4 cats would kill 4 mice in how many days ?