A bicycle pump contains 250cm3 of air at a pressure of 90kPa. If the air is compressed , the volume is reduced to 200cm3. What is the pressure of the air inside the pump?

Answer 1

P V = n R T
if n , R and T are constant then
P1 V1 = P2 V2
P2 = P1 (V1/V2)

Assuming that T is constant is needed but unreliable because in real life the pump will heat up.