Final answer:
To find the percentage more boys than girls, divide the difference between the number of boys and girls by the number of girls and multiply by 100.
Step-by-step explanation:
To find the percentage of boys compared to girls, you need to calculate the difference in the number of boys and girls and then express it as a percentage. In this case, there are 240 boys and 400 students in total, so the number of girls is 400 - 240 = 160. The difference between the number of boys and girls is 240 - 160 = 80. To find the percentage more boys than girls, divide the difference (80) by the number of girls (160) and multiply by 100.
Percentage difference = (80 / 160) * 100 = 50%.
Therefore, there are 50% more boys than girls in the school hall.