Say the consumption per day for eating = x kg./day, so for the first case, Total oil= 50*(11+x) kg.; and for the second case, Total oil= 45*(15+x) kg..

Since 50*(11+x) = 45*(15+x) => x = 25 kg/day;

So, the oil will past for 50*[(11+25)/25] = 50*(36/25)=72 days.

Option A.