Question

There are 40 students in a class, out of them 15 are boys. The mean of marks obtained by boys is 33 and that for girls is 35. Find out the mean of all students in the class.

Answer 1

Total number of students = 40 

Number of boys =15 

∴ Number of girls = 40 – 15 = 25 

The mean of marks obtained by 15 boys is 33 

Here, sum of the marks obtained by boys = 33 x 15 

= 495 …(i)

The mean of marks obtained by 25 girls is 35 Sum of the marks obtained by girls 

= 35 x 25 

= 875 …(ii) 

Sum of the marks obtained by boys and girls 

= 495 + 875 … [From (i) and (ii)] = 1370 

∴ Mean of all the students

= 34.25 

∴ The mean of all the students in the class is 34.25.