Correct Answer - Option 4 : 110
Given
Total students = 550
Ratio of boys and girls = 6 : 5
Calculation
Number of boys = 550 × (6/11) = 300
Number of girls = 550 × (5/11) = 250
Let the number of girls joining the class be x.
Now,
300/(250 + x) = 5 : 6
⇒ 250 + x = 300 × (6/5)
⇒ 250 + x = 360
⇒ x = 360 - 250 = 110
∴ The required girls is 110.