as subject.

Explanation

ATQ, Total number of students in the class = 1000 Number of students studying Maths subject = 0.2 x 1000 = 200 Number of boys studying Maths subject = 200 x (3/10) = 60 Number of girls Studying Maths = 200 – 60 = 140 Let the number of boys studying Chemistry be 'x' Therefore, number of girls studying Chemistry = 0.875x Total number of students studying Chemistry = 1.875x Total number of students studying Physics = 1.875x/0.6 = 3.125x Therefore, 3.125x + 1.875x = 1000 – 200 Or, 5x = 800 Or, x = 160 Therefore, total number of students Studying Physics = 3.125x = 500 Number of boys Studying Physics = {(500 + 100)/2} = 300 Number of girls Studying Physics = 500 – 300 = 200 Number of students Studying Chemistry = 1.875x = 300 Number of boys Studying Chemistry = 160 Number of girls Studying Chemistry = 300 – 160 = 140 Therefore, Required difference = 160 – 140 = 20