Vinod ranked 36th from the top and 18th from the bottom in his class. How many students are there in his class?

Given: 

Vinod ranked 36th from the top and 18th from the bottom in his class.

Total students = Rank from top + Rank from bottom − 1

Total = 36 + 18 − 1 = 53

So, 53 students are there in his class.

Thus, correct option is (b).