Let's convert the distance in meters first:
[tex]d=34 km=34000 m=3.4 \cdot 10^4 m[/tex]
The sound wave travels at speed
[tex]v=340 m/s[/tex]
So we can use the basic relationship between space, time and velocity to calculate the time it takes for the sound to reach our ears:
[tex]t= \frac{S}{v}= \frac{3.4 \cdot 10^4 m}{340 m/s}=100 s [/tex]
