SOLUTION: The average age of boys & girls in a class is 10.5 yrs. That of the boys is 10.6 & that of the girls is 10.1. If there are 60 boys in the class how many girls are there?

Question 323609: The average age of boys & girls in a class is 10.5 yrs. That of the boys is 10.6 & that of the girls is 10.1. If there are 60 boys in the class how many girls are there?
Found 2 solutions by mananth, Fombitz:
Answer by mananth(16946) (Show Source): You can put this solution on YOUR website!
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
Answer by Fombitz(32388) (Show Source): You can put this solution on YOUR website!
Let B be the sum of ages of the boys, G sum of ages of the girls.
Let Nb be the number of boys, Ng be the number of girls.
1.
2.
3.

Then from eq. 1,

From eq. 2,

Substitute into eq. 3,

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