A sample of gas has its number of molecules halved, its Kelvin temperature doubled, and its volume halved. What is the new pressure, relative to the original pressure?

Answer 1

P V = n R T
well, R does not change :)
R = P V/(nT) = P' .5V /(.5n 2T) = P'(.5)V/(nT)
so
.5 P' = P
P' = 2 P