Read the question below:
What is the average age of Aman, Boman and Chaman?
Read the statement given below:
The age of Aman, Boman and Chaman are in the ratio 6 : 5 : 3 respectively.
Which of the below information is additionally required to answer the above question?

​​Given:

Their ages are in the ratio 6 : 5 : 3

Aman = 6x, Boman = 5x, Chaman = 3x

 Now evaluate each option to see which gives us a specific value of x:

The age of Boman is greater than the average age of three people.

 5x > 6x + 5x + 3x /3

but it doesn’t give a specific value of x

The difference in the age of Boman and Chaman is twice the difference in the age of Aman and Boman.

(5x - 3x) = 2 × (6x - 5x)
2x = 2 × 1x → 2x = 2x 
Still doesn’t give a specific value of x

The age of Aman is twice the age of Chaman.

Aman = 6x
Chaman = 3x
→ 6x = 2 × 3x → 6x = 6x 
Still doesn’t give a specific value of x

Option D: On the first birthday of Chaman, Aman was 9 years older than Boman

Aman = 6x - (3x - 1) = 3x + 1

Boman = 5x - (3x - 1) = 2x + 1

Now apply the given condition:
Aman was 9 years older than Boman

→ (3x + 1) = (2x + 1) + 9
→ 3x + 1 = 2x + 10
→ x = 9 

Now we can find actual ages and their average:

Aman = 6x = 54, Boman = 5x = 45, Chaman = 3x = 27

Average = (54 + 45 + 27) / 3 = 126 / 3 = 42 (Follow)