A helium-filled balloon escapes a child's hand at sea level and 23.0 C. When it reaches an altitude of 3000 m, where the temperature is 4.4 C and the pressure is only 0.71 atm, how will its volume compare to that at sea level?
It will be 1.5 times larger.
The altitude itself is irrelevant. The ideal gas law states
Therefore, the volume at 3000m is 1/0.665 = 1.5 times larger than at sea level.