One Hundred Millilitres of Water Is Poured into a U-Tube

Short Answer

One hundred millilitres of water is poured into a U-tube that has a cross-sectional area of 1 cm². Then 100 millilitres of oil, with a density 80% that of water, is poured down one side of the U-tube so that the oil floats on the water. Find the difference in height of the liquid surfaces on the two sides of the U-tube.