N = the number of terms

S = the sum of the numbers in the set.

Average = S/N

For example

The marks of a student in five subjects are 96, 94, 92, 87, and 81, then what is the average score of the student?

N = 5

S = 96 + 94 + 92 + 87 + 81 = 450

A = 450/5 = 90.

*Another type questions*

1). There are 36 boys and 44 girls in a class. The average score of boys is 40 and girls are 35. Then what will be the average mark?

Total mark of 36 boys = 36 x 40 = 1440

Total mark of 44 girls = 35 x 44 = 1540

Total mark of 80 Students = 1440 + 1540 = 2980

Average mark of the class = (2980 / 80)

= 37.25

2). The average weight of 15 members in a football team is 24 kg when a new member included, the average weight increases by 2. What is the weight of the new member?

Total weight of 15 member = 24 x 15 = 360

Average after including a new member = 24 + 2 = 26

Total weight of 16 member = 26 x 16 = 416

Weight of the new member = Total weight of 16 member - Total weight of 15 member

= 416 - 360

= 56.