The number of students in classes A and B are 60 and 70, respectively. The average score in mathematics of students in class B is 57 and that of all students in classes A and B is 63. What is the average score of students in class A?

70

Let average score of students in class A = A

ATQ ,

60 × A + 70 × 57 = 130 × 63

60A + 3990  = 8190

60A  = 4200

A = 70

So , average score of students in class A = 70