Question 802215
The ratio of boys and girls in a school is 3 : 2 .
 When 6 more girls join, this ratio becomes 6 : 5 .
 Then the number of boys in the school is
:
Let x = the multiplier
then
3x = no. boys
2x = no. of girls originally
:
When 6 girls added:
{{{(3x)/(2x+6)}}} = {{{6/5}}}
Cross multiply
5(3x) = 6(2x+6) 
15x = 12x + 36 
15x - 12x = 36
3x = 36
x = 36/3
x = 12 is the multiplier
therefore
3(12) = 36 boys
:
:
Check this
2(12) = 24 girls originally
then 30 girls when six added
{{{36/30}}} = {{{6/5}}}