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 halfempty, 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
Answer (as printed): B
Explanation
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 ;
Explanation as extracted from the printed page; notation may be imperfect.