The concentration of petrol in three different mixtures (of petrol and kerosene) is $$\frac{1}{2}, \frac{3}{5}$$ and $$\frac{4}{5}$$ respectively. If 2 litres, 3 litres and 1 litre are taken from these three different vessels and mixed, what is the ratio of petrol and kerosene in the new mixture?

Quantity of Petrol in the mixture,

= $$\frac{1}{2}$$ x 2 + $$\frac{3}{5}$$ x 3 + $$\frac{4}{5}$$ x 1

= $$1 + \frac{9 + 4}{5}$$

= $$\frac{18}{5}$$

Quantity of kerosene in the mixture,

= $$\frac{1}{2}$$ x 2 + $$\frac{2}{5}$$ x 3 + $$\frac{1}{5}$$ x 1

= $$1 + \frac{6 + 1}{5}$$

= $$\frac{12}{5}$$

Ratio of petrol and kerosene in the mixture,

= $$\frac{18}{5} : \frac{12}{5}$$

= $$3 : 2$$

Hence, option B is the correct answer.