Given :
volume of an ideal gas is reduced by 20% keeping temperature constant
solution :
by using ideal gas equation ,
PV=nRT
aas nRT is constant so whole PV is constant
PaVa=PbVb
⇒ PaVa=Pb[Va−20100Va]
⇒ Pa=Pb[45]
⇒ percentage change in pressure is equals to
Pb−PaPa X 100
⇒ Pb−45Pb45Pbx 100
⇒ 25%
hence the correct option is:D