The total number of students in school A to school B is in the ratio 4:5. The number of boys in school A is 20% less than the number of boys in school
B. The number of girls in school B is 300 more than that in school
A. If the average number of students in schools A and B is 3150, find the difference between the number of boys and girls in school
A.

ATQ, Total students in schools A and B = 3150 * 2 = 6300 Total students in school A = 6300 * 4/9 = 2800 Total students in school B = 6300 – 2800 = 3500 Let the number of girls in schools A and B be x and (x + 300) respectively. 20% less ⇒ boys in A = 80% of boys in B Let the number of boys in school B be 5y. Then boys in school A = 5y * 80/100 = 4y So, x + 4y = 2800 ---(1) 5y + (x + 300) = 3500 x + 5y = 3200 ---(2) (2) – (1): (x + 5y) – (x + 4y) = 3200 – 2800 y = 400 From (1): x + 4*400 = 2800 x + 1600 = 2800 x = 1200 Number of boys in school A = 4 * 400 = 1600 Number of girls in school A = 1200 Required difference = 1600 – 1200 = 400