Okay, I finally got it. I thought it was very complicated and tried to solve it in a complicated manner! 1. Pour the mixture from the original container (60 L) to 7 L container and transfer that 7 L to 43 L container. Repeat it. At this point, the 43 L container has 14 L of oil. 2. Now, the trickiest part: Pour the oil from the original container to 11 L container. And, pour the 11 L container, which is full, to 7 L container. Now the 11 L container has 4 L oil (11-7=4). 3.Pour that 4 L water to the 43 L container where there is already 14 L of oil. Now it is altogether 18 L of oil in 43 L container. 4. Repeat step #2 three more times, which will result in 12 L of oil (4*3=12)!!! So altogether 18 + 12 = 30 L of oil in 43 L Container. And, at the same time 30 L of water is left in the original 60 L container. Yes!!! Finally! :) :D