There are several information's already given in the question. Based on the information's the answer can be easily deduced.
We know the formula
<span>P1*V1/T1 = P2*V2/T2 </span> As the temperature is constant, so T1 and T2 can be negated. The formula changes to <span>P1*V1 = P2*V2 </span>70 * 1 = 540 * V2 270/540 = V2 <span>V2 = 0.5 </span> From the above deduction, we can conclude that the new volume is 0.5 liters. I hope that the procedure is clear enough for you to understand.