Final answer:
The tank would be filled in 30 minutes if both keys are opened simultaneously.
Explanation:
When both keys are opened simultaneously, they complement each other's filling speeds. The first key fills the tank in 10 minutes, while the second key does it in 30 minutes. To combine their efforts, you need to find the smallest common multiple of 10 and 30, which is 30 minutes. Therefore, the tank would be filled in 30 minutes if both keys are opened simultaneously.
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