Question 323609
let the number of girls be x
Number of boys = 60
Total students = x+60
Average age of class = 10.5
The total age of the class = 10.5(x+60)
..
Average age of girls = 10.1
total age of girls = 10.1x
..
Average age of boys = 10.6
Number of boys = 60
Total age of boys = 10.6*60= 636 years
..
Total age of girls + total age of boys = Total age of class
10.1x+636=10.5(x+60)
10.1x +636=10.5x + 630
10.5x-10.1x = 636-630
0.4x= 6
x= 6/0.4
Multiply by 10 and divide by 10
x=60/4
x=15 girls