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 pumps add kerosene, which is 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 ?

Given that the Capacity of Kerosene=(18/900)*1000=20km/ltr

Cost of Petrol=Rs.30/ltr(Given)

Cost of Kerosene=2/3(Cheaper than Petrol)=1/3 (Petrol)=Rs.10/ltr

Let the Quantity of Kerosene is x ltr in 1 ltr of mixture

 Capacity of Kerosene=20km/ltr

Capacity of Petrol=40km/ltr

If there is x Ltr Petrol in 1 Ltr

Then,

20(x)+40(1-x)=38

x=0.1 ltr

Cost of mixture = 10(.1) +30(.9)=Rs.28

The Cost of Petrol which I gave was Rs.30 but the Original Amount is Rs.28

Hence the Additional Amount that the Pump Owner was Charging =Rs.30-Rs.28=Rs.2