Question

a man takes 100 rs and go to a shop and he bought 75 rs object and the shopkeeper gave me only 5 rs . why?

Answer 1

Simple.
because he was out of his mind.

Answer 2

First of all the attachment you have mentioned in the question,

it is definetly not an IAS level question,

But,

Since the question is asked there might be some logic to it, so i am assuming the most probable logic could be

The shopkeeper charged 26.67% GST or ant other tax for the product

So,

The item costed 75 rupees,

26.67% of 75 = 20 rupees

So,

Total cost = 75 +20 =95 rupees

So,

The change returned by him = 100-95 = 5 rupees