Question

Class A of 20 students scored 60% while class B undergoing the same test scored 70%. It was decided to put all marks together and find the common average

Answer 1

Not enough info, since we don't know how many students are in Class B.

Answer 2

Class B has 28 students

Answer 3

Sorry

Answer 4

@mathstudent55

Answer 5

You can't take an average of the averages since each class has a different number of students.
The way you find the average grade of a number of students is by taking the total number of points scored by all students and dividing by the number of students.
If a class has 20 students, and the average score was 60, what was the total number of points scored by all students combined?
To find that, multiply the average score by the number of students.
Then do the same for the class of 28 students. Multiply the average by the number of students.
Then add the total score of each class, so you have the total score of all 48 students.
Then divide the total score of all students in both classes by 48.