I think this is what you are looking for...
0.8 = 80%
100 = 20%
80/20 = 4
100 x 4 = 400 boys
All children (girls/boys) learn at school
Divide the number of girls by the total number of children (boys + girls).
189 boys
4/5 of the children are boys. So 1 - 4/5 ie 1/5 of the children are girls. 1/5 = 100 so 1 = 500 ie there are 500 children in all. 4/5 of 500 is 500*4/5 = 400 So there are 400 boys.
Most children attend school, more boys than girls though
138
153
The answer depends on whether the children are picked at random. If they were selected from inside a girls' school the probability should be quite close to 0. Likewise, if the children were picked inside a boys' school. If six children are picked at random from a large group of children with an equal number of boys and girls, then the answer is 6C2*(1/2)6 = 15/32 = 0.47, approx.
72 girls and 18 boys for a total of 90.
699
Probability
Yes! And it is the law of most countries. Children have to go to school.