The sound of an explosion on the surface of a lake is heard by a boatman 100 m away and by a diver 100 m below the point of explosion.
Who will hear the sound of explosion first?

Explanation

To determine who hears the sound of the explosion first—the boatman on the surface of the lake or the diver 100 meters below the surface—we need to calculate the time it takes for the sound to reach each of them.

### Step 1: Understand the scenario
- The explosion occurs at the surface of the lake.
- The boatman is 100 meters away horizontally from the explosion.
- The diver is 100 meters vertically below the explosion.

### Step 2: Identify the speeds of sound in different mediums
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