Maths
posted by Surya .
A moment ago, 80% of the children in a hall were girls. 48 girls and 2 boys left the hall. The remaining children were then told to form groups of 9. In each group, there were 2 boys. How many children were there in the hall first?

initially, b/g = 1/4
after some left, (b2)/(g48) = 2/7 since there were groups of 2 boys and 7 girls.
g=4b
7(b2) = 2(4b48)
b = 82
so g = 328
so, at first there were 410 children
after kids left, there were
80 boys
280 girls
making 40 groups of 2boys and 7girls 
Dear Steve,
Thank you very much for your kind help.
Can understand clearly.
With regards,
Surya 
Martha spent 4/a of her allowance on food and shopping.what fraction of her allowance had she
left