At a pressure 42 kPa, the gas in a cylinder has a volume of 11 liters. Assuming temperature remains the same, if the volume of the gas is decreased to 9 liters, what is the new pressure?

Boyle's law is a gas law, stating that the pressure and volume of a gas have an inverse relationship, when temperature is held constant. That is PV = constant. Therefore, (PV) initial = (PV) final. 42x11 = 9x P (final). P (final) = 42x11/9 = 51.34kPa.