**P. 3919.** There is a vertical cylinder filled with a sample of ideal gas in a thermostat. A horizontal piston which can move easily, splits the cylinder into two parts. The volume of the upper part is 4 times as much as the volume of the part below. If the cylinder is placed to a thermostat at a temperature of 400 K the ratio of the volumes of the upper and lower parts will be 3:1. Find the ratio of the number of molecules of the gas in the two parts of the cylinder.

(4 points)

**Deadline expired on 13 November 2006.**