AFCAT Model Paper 7

Given:
The average marks scored by boys in a class are 72
Average marks of all 40 students = 75
Number of girls in the class = 25
Formula Used:
Average = Sum of observations/Number of observations
Calculation:
There are 40 students in class, out of which 25 are girls
⇒ Number of boys = 40 - 25 = 15
Average marks of boys = 72
Sum of marks of all boys = Number of boys × Average marks of boys
⇒ 15 × 72 = 1080
Now, Sum of marks of all students = Number of students × Average marks of all students
⇒ 40 × 75 = 3000⇒ Sum of marks of girls = sum of marks of all students – sum of marks of boys
⇒ 3000 – 1080 – 1920
Average marks of girls = sum of marks of girls/number of girls
⇒

1920

25

=76.8
∴ The average mark of girls in the class is 76.8.