My Scooty gives an average of 40 kmpl of petrol. But after recent filling at the new petrol pump, its average dropped to 38 kmpl. I investigated and found out that it was due to adulterated petrol. Petrol pimps add kerosene, which is $\frac{2}{3}$ cheaper than petrol, to increase their profits. Kerosene generates excessive smoke and knocking and gives an average of 18 km per 900 ml. If I paid Rs. 30 for a litre of petrol, What was the additional amount the pump-owner was making?

A. Rs. 1.75

B. Rs. 1.80

C. Rs. 2

D. Rs. 2.30

Let x ml of kerosene be there in 1 litre mixture. Then, quantity of petrol in 1 litre mixture = (1000 – x) ml $\begin{array}{l}\therefore\frac{40}{1000}(1000-x)+\frac{18}{900}x=38\\ \Rightarrow\frac{x}{25}-\frac{x}{50}=2\\ \Rightarrow\frac{x}{50}=2\\ \Rightarrow x=100\end{array}$ So, 1 litre mixture has 900 ml petrol and 100 ml kerosene. Cost of 1 litre petrol = Rs. 30 Cost of 1 litre kerosene $\begin{array}{l}=\text{ Rs. }\left[\left(1-\frac{2}{3}\right)\times30\right]\\ =\text{ Rs. }10\\ \text{Coast of 1 litre mixture}\\ =\text { Rs. }\left(\frac{30}{1000} \times 900+\frac{10}{1000} \times 100\right) \\ =\text { Rs. } 28 \end{array}$ ∴ Additional amount earned by pump-owner = Rs. (30 – 28) = Rs. 2