Final answer:
The scuba cylinder will last approximately 30 minutes at a depth of 20 meters.
Step-by-step explanation:
To determine how long a scuba cylinder will last at a specific depth, we need to consider factors such as pressure and consumption rate. The scuba cylinder will last approximately 30 minutes at a depth of 20 meters. At sea level, the pressure is 1 atmosphere (atm), and the cylinder lasts for 2 hours.
When the depth is 20 meters (66 feet), the pressure increases to around 3 atmospheres (2 atms of water pressure plus 1 atm of atmospheric pressure). Generally, the consumption rate also increases with depth. Assuming a linear relationship, the cylinder will last around 30 minutes at this depth.