What is the value of x in the above table

Consider the following date:

What is the value of x in the above table?

Answer: A

Method I

Let the number of girls be g and number of boys be b.

Overall average marks in English = Total marks in English / Total Students = (9g + 8b) / (g + b) = 8.8

9g + 8b = 8.8g + 8.8b

0.2g = 0.8b

g = 4b

Similarly, Overall average marks in Hindi = Total marks in Hindi / Total Students = (8g + 7b) / (g + b) = x

Putting value of g from,

(8 × 4b + 7b) / (4b + b) = x

39b/5b = x

x = 7.8

Method II

Average marks of girls and boys in English are 9 and 8 respectively, while the overall average is 8.8.

By allegation method:

So, ratio of girls and boys = 0.8 : 0.2 = 4 : 1

So, x = [(4 × 8) + (1 × 7)] / (4 + 1)

= 39/5

= 7.8