A tank is filled with water up to a height \(H\). Water is allowed to come out of a hole \(P\) in one of the walls at a depth \(D\) below the surface of water. Express the horizontal distance \(x\) in terms of \(H\) and \(D\)（ ）
Under the condition that the temperature remains constant, the volume of gas is inversely proportional to its pressure. If the volume of gas is \(630\) cubic centimetres at a pressure of \(360\;mm\) of mercury, then what will be the pressure of the gas if its volume is \(720\) cubic centimetres at the same temperature?