A column of mercury of 10cm length is contained in the middle of a narrow horizontal 1m long tube which is closed at both the ends. Both the halves of the tube contain air at a pressure of 76 cm of mercury. By what distance will the column of mercury be displaced if the tube is held vertically?

A column of mercury is in the middle of horizontal tube of uniform cross section closed at both ends. The pressure of the enclosed air column on either side of the mercury is 75 cm of mercury column. When the tuve is placed vertical the length air below the mercury column is (3)/(5) th of that above it. if length of mercury column is 10n cm. find n.