It does not matter how many students are actually in the engineering college because we are working with percentages of whatever number of students there were. So let's say there were 100 students for the purposes of this problem. That means there are 60 boys and 40 girls.
If 30% of the boys received an A grade, that means there were 18 boys who received an A, and similarly there were 8 girls that received an A grade. So a total of 26 students received an A. The ratio of boys to the total of A grades is: 18/26, so the probability of a randomly selected A grade student being a boy is: 9/13 or approximately 0.6923
