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.**