There are 20 students in a Chemistry class and 30 students in a Physics class. Find the number of students which are either in Physics class or Chemistry class in the following case : the classes meet at the same hour.

There are 20 students in a Chemistry class and 30 students in a Physics class. Find the number of students which are either in Physics class or Chemistry class in the following case : the two classes meet at different hours and ten students are rolled in both the subjects.

The set of poor students in the class is :

The set of weak students in a class is :

The distribution below gives the weights of 30 students of a class. Find the median weight of the students.

Which of the following is not a class of proteins ?

There are 20 girls and 15 boys in a class. What is the ratio of number of girls to the total number of students in the class?