To determine the volume of air at 100 psi in a 1 cubic foot tank pressurized to 5000 psi, the ideal gas law can be applied. The relationship between pressure and volume indicates that as pressure increases, the volume of gas decreases proportionally. At 5000 psi, the tank contains significantly more air than it would at 100 psi due to compression. Calculating the exact volume at 100 psi requires converting the pressures into a common unit and applying the formula for gas laws. Understanding these principles is essential for accurate air tank calculations.