Question: In a class of 100 students the mean marks obtained in a certain subject is 30 and in another class of 50 students the mean marks obtained in the same subject is 60. The mean marks obtained by the students of two classes taken together is:

a) 40

b) 45

c) 48

d) 50

Answer: total marks obtained by students of first class = 100×30 =3,000.

total marks obtained by students of another class = 50×60 =3,000.

total marks obtained by students of both classes =3,000 + 3,000 =6,000.

total number of students = 100+50 =150.

mean mark = 6000/150 =40.