[填空题]
A helium-filled balloon escapes 0qvsz3v7 vr;edpq) e1a child’s hand at se n8/d9*acio p7vc ele2a level and 20.0 $^{\circ} $ C. When it reaches an altitude of 3000 m, where the temperature is 5.0 $^{\circ} $ C and the pressure is only 0.70 atm, how will its volume compare to that at sea level? times the original volume