To determine how long the submarine rose during stage 2 in minutes, we need to follow these steps:
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Calculate the initial depth of the submarine: The submarine is initially at 925 feet below sea level.
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Calculate the rise in stage 1: In stage 1, the submarine rises 20% of its initial depth. \[ \text{Rise in stage 1} = 0.20 \times 925 = 185 \text{ feet} \]
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Calculate the new depth after stage 1: After rising 185 feet, the new depth is: \[ 925 - 185 = 740 \text{ feet below sea level} \]
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Determine the final depth: The submarine's final depth is 200 feet below sea level.
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Calculate the total rise needed to reach the final depth: The total rise required from the depth after stage 1 to the final depth is: \[ \text{Rise needed} = 740 - 200 = 540 \text{ feet} \]
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Calculate the time taken in stage 2: In stage 2, the submarine rises at a rate of 13.5 feet per minute. Thus, the time taken for stage 2 is: \[ \text{Time} = \frac{\text{Rise needed}}{\text{Rate}} = \frac{540}{13.5} \]
Performing the calculation: \[ \text{Time} = \frac{540}{13.5} = 40 \text{ minutes} \]
So, the submarine rose for 40 minutes during stage 2.