22.41 seconds longer
From the question give;
Speed of sound in air at 20°C is 343 m/s
Speed of sound in water at 20°C is 1,483 m/s
We are given a distance of 10 Km or 10,000 m
We need to finder how much longer it will take for the sound to travel in air.
Time = Distance ÷ Speed
Therefore;
Time taken in Air = Distance ÷ speed of sound in air
= 10000 m ÷ 343 m/s
= 29.15 seconds
Time taken in water = Distance ÷ speed of sound in water
= 10,000 ÷ 1,483 m/s
= 6.74 seconds
Difference in time = 29.15 seconds - 6.74 seconds
= 22.41 seconds
Therefore, it takes 22.41 seconds longer for sound to travel through air than water.