If cost of a 200 ml soft drink is ₹20, then what is the cost of 1 litre of soft drink?

The correct option is D ₹100
Ratio of quantity to its cost is constant.
We know, 1 litre = 1000 ml

Let $x$ be the price of 1 litre coke

therefore $\frac{200}{20}$ = $\frac{1000}{x}$

$\therefore x=\frac{1000\times 20}{200}=₹100$