Let the capacity of the fuel tank = 100 litres
When Ist time B type petrol was filled then A and B types petrol were 50 litre each.
Again when A type petrol was filled in half empty tank then A type and B type were 75 litres and 25 litres respectively.
Hence, their ratio were 3 : 1
Again, when tank was half empty, then
Amount of A type petrol =
×50 = 37.5 litres
& Amount of B type petrol =
×50 = 12.5 litres
Then tank was filled with B type petrol in half empty tank.
Since, Amount of B type petrol = 12.5 + 50 = 62.5 litres
Hence, percentage of A type petrol at present in the tank is 37.5%.