Asample of hydrogen gas at 2.0 atmospheres and 273 k occupies a volume of 5.0 liters. the gas sample is completely transferred to a 10.0-liter sealed, rigid container. what is the new pressure of the gas sample when the temperature returns to 273 k?

Boyle's law gives the relationship between pressure and volume of gas, It states that for a fixed amount of gas when the temperature is kept at a constant value, pressure is inversely proportional to volume of gas.
PV = k
where P - pressure, V - volume and k - constant 
p1v1 = p2v2
where parameters for the first instance are on the left side and parameters for the second instance are on the right side of the equation 
2.0 atm x 5.0 L = P x 10.0 L 
P = 1.0 atm
new pressure is 1.0 atm