During the petrol transporting from one plant to another, the fuel tanker ever wasted 10 litres of petrol.
The process of filling the tank at one plant and discharging petrol from its bottom at another is monitored very carefully.
All holes of the fuel tanker were thoroughly filled, and it was accompanied by a reliable guard during their journey.
But still, the discharge of fuel always lacked exactly 10 litres.
Where did the petrol disappeare?