Explanation:
total number of student = 900
number of girls = 300
1) to find the number of boys
number of boys = total no. of students - no. of girls
= 900 - 300
= 600
2) to find the ratio of boys and girls
ratio of boys and girls = no. of boys : no. of girls
= 600 : 300
= 200
3) ratio of boys and total no. of students
= 600 : 900
= 200: 300
= 2:3
4) ratio of girls and total no. of students
= 300 : 900
= 1:3
5)ratio of girls and boys
= 300 : 600
= 1:2