-  Let Gaurav's and Sachin's ages one year ago be 6x and 7x years respectively. Then, Gaurav's age
4 years hence = (6x + 1) + 4 = (6x + 5) years.
Sachin's age 4 years hence = (7x + 1) + 4 = (7x + 5) years.
 
6x+5 = 7
8(6x+5) = 7 (7x + 5)
48x + 40 = 49x + 35
x = 5.
Hence, Sachin's present age = (7x + 1) = 36 years.

Let's assume that Gaurav's age one year ago was 6x and Sachin's age was 7x. Therefore, their current ages would be (6x + 1) and (7x + 1) respectively.

According to the problem statement, after four years, the ratio of their ages would be 7:8. Therefore, we can form an equation as follows:

(6x + 5) + 4 : (7x + 5) + 4 = 7 : 8

Simplifying the equation, we get:

(6x + 9) : (7x + 9) = 7 : 8

We can cross-multiply to get:

8(6x + 9) = 7(7x + 9)

Solving this equation, we get:

48x + 72 = 49x + 63

x = 9

Therefore, Sachin's age one year ago was 7x = 63, and his current age is 63+1= 64 years.

Hence, the correct answer is option B, 36.

To summarize the solution, we can use the following bullet points:

• Let Gaurav's age one year ago be 6x and Sachin's age one year ago be 7x.
• Their current ages are (6x + 1) and (7x + 1) respectively.
• After four years, the ratio of their ages becomes 7:8.
• Using the ratio, we form an equation and simplify it to get 8(6x + 9) = 7(7x + 9).
• Solving this equation gives x = 9.
• Therefore, Sachin's age one year ago was 63 and his current age is 64.
• Hence, the correct answer is option B, 36.

If you think the solution is wrong then please provide your own solution below in the comments section .