From the condition, the scores earned by all girls were 83G, where G is the number of girls. The scores, earned by boys, were 71B, where B is the number of boys. Also, we are given that= 80, which implies 83G + 71B = 80G + 80B, or 3G = 9B, or G = 3B. Thus among each 4 persons there is 3 girls and 1 boy. The percentage of girls among all students is 75%.