An empty fuel tank of a car was filled with A type petrol. When the tank was half-empty, it was filled with B type petrol. Again when the tank was half-empty, it was filled with A type petrol. When the rank was half-empty again, it was filled with B type petrol. What is the percentage of A type petrol at present in the rank ?

Let the capacity of the tank be 100 litres
Initially: A type petrol = 100 litres

After first operation:
A type petrol = $$\frac{100}{2}=50$$ litres
B type petrol = $$50$$ litres

After second operation:
A type petrol = $$50+\frac{50}{2}=75$$ litres
B type petrol = $$\frac{50}{2}=25$$ litres

After third operation:
A type petrol = $$\frac{75}{2}=37.5$$ litres
B type petrol = $$50+\frac{25}{2}=62.5$$ litres

$$\therefore$$ Required percentage = 37.5%

=> Ans - (B)