Answer :
Assume that the gas is an Ideal gas.
P V = n R T = constant
P₁ V₁ = P₂ V₂
V₂ = P₁ V₁ / P₂ = 1 atm * 100 cc / 4 atm = 25 cc
P V = n R T = constant
P₁ V₁ = P₂ V₂
V₂ = P₁ V₁ / P₂ = 1 atm * 100 cc / 4 atm = 25 cc