A class consists of 50 students out of which 30 are girls, the mean of mark scored by girls in a test is 45 and that of boys is 30. determine the mean score of the whole class.

There are 50 students in a class, of which 40 are boys. The average weight of the class is 44 kg and that of girls is 40 kg. find the average weight of the boys.

In a school, there are 1000 students, out of which 430 are girls. It is known that out of 430, 10% of the girls study in class XII. What is the probability that a student chosen randomly studies in Class XII given that the chosen student is a girl?

20 % of 25 students in a class are boys.How many girls are in the class?

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?

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.

There are 40 scholars in a class, out of which 10 are sports- persons. Three scholars are selected at random out of them. Find the probability distribution for the selected persons who are sports-persons. Find the mean of the distribution.

A class consists of 10 boys and 8 girls. Three students are selected at random. Find the probability that the selected group has : all girls.