A narrow cylindrical tube of length L, closed at one end, comprises air, separated from the outer column length h of mercury. The tube is open end up. What is the length of the air column in the tube, if the tube turning into an open end of the tube down poured half of the mercury?

Detailed solution with a short recording conditions, laws and formulas used in the decision, the withdrawal of the calculation formula and the answer.
If you have any questions about the decision to write. I try to help.