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1. 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

Solution:

Let x ml of kerosene be there in 1 litre mixture.
Then, quantity of petrol in 1 litre mixture = (1000 - x) ml

∴ \frac{40}{1000} (1000 - x)

+ \frac{18}{900} x

= 38

\begin{aligned} \Rightarrow \frac{x}{25} - \frac{x}{50} = 2 \\ \Rightarrow \frac{x}{50} = 2 \\ \Rightarrow x = 100 \end{aligned}

So, 1 litre mixture has 900 ml petrol and 100 ml kerosene.
Cost of 1 litre petrol = Rs. 30
Cost of 1 litre kerosene
= Rs.

[(1 - \frac{2}{3}) \times 30]

= Rs. 10
Coast of 1 litre mixture
= Rs.

(\frac{30}{1000} \times 900 + \frac{10}{1000} \times 100)

= Rs. 28
∴ Additional amount earned by pump-owner
= Rs. (30 - 28)
= Rs. 2

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