Correct Answer - Option 1 : 7.8

**Formula used :**

Average = Sum of all values/Number of values

**Calculations :**

Let the number of girls be 'g'

Let the number of boys be 'b'

Total number of boys and girls = b + g

Total marks of girls in English = 9 × g = 9g

Total marks of boys in English = 8 × b = 8b

Total marks in English 9g + 8b

According to the question

⇒ 8.8 = (9g + 8b)/(b + g)

⇒ b : g = 1 : 4

Number of boys = x and number of girls = 4x

Total number of boys and girls = x + 4x = 5x

Now, total marks in Hindi

Marks of girls in Hindi = 8 × 4x = 32x

Marks of boys in Hindi = 7 × x = 7x

Average of marks in Hindi = (32x + 7x)/5x (total marks = 32x + 7x)

⇒ 7.8

**∴ The average marks in Hindi will be 7.8.**