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 tank was half-empty again, it was filled with B type petrol. What is the percentage of A type petrol at present in the tank ?

A. 33.5%

B. 37.5%

C. 40%

D. 50%

Answer: Option B

Solution(By Examveda Team)

Let the capacity of the tank be 100 litres.
Then,
Initially :
A type petrol = 100 litres
After first operation :
A type petrol = $$\left( {\frac{{100}}{{2}}} \right)$$ = 50 litres ;
B type petrol = 50 litres
After second operation :
A type petrol = $$\left( {\frac{{50}}{2} + 50} \right)$$  = 75 litres ;
B type petrol = $$\left( {\frac{{50}}{2}} \right)$$ = 25 litres
After third operation :
A type petrol = $$\left( {\frac{{75}}{2}} \right)$$ = 37.5 litres
B type petrol = $$\left( {\frac{{25}}{2} + 50} \right)$$  = 62.5 litres
∴ Required percentage = 37.5%