Question

A sample of helium gas is placed in a rigid cylinder that has a movable piston. The volume of the gas is varied by moving the piston, while the temperature is held constant at 273 K. The volumes and corresponding pressures for three trials are measured and recorded in the data table below. For each of these trials, the product of pressure and volume is also calculated and recorded. For a fourth trial, only the volume is recorded.
State evidence found in the data table that allows the product of pressure and volume for the fourth trial to be predicted.

Answer 1

Helium is a light gas.  Movement can be predicted by which chamber has the lighter gas(es) and which chamber has the heavier.  constant changes can also be a variable.  If the gas is constant, then changes are more easily predicted.

Answer 2

P x V = 0.412
New V = 1.373 L
0.412L x atm/ 1/373 L = 0.3 atm