Answer: 220
Step-by-step explanation:
Given : The ratio of boys to girls at a school is 9 to 11.
Let the number of boys be 9x and the number of girls be 11x.
Since there are 400 students attend the school.
Then we have the following equation :-
[tex]9x+11x=400\\\\\Rightarrow\ 20x=400\\\\\Rightarrow\ x=\dfrac{400}{20}=20[/tex]
Now, the number of girls = 11x = 11(20)=220
Hence, there are 220 girls.
