Solving Sound Waves Problem: Distance of Explosion from Ground Vibration

[moronto]

Homework Statement

The speed of sound along the ground is about 6.75 km/s while the speed of sound in air is 342 m/s. A very powerful explosion occurs some distance away and you feel the ground vibrate 74.0 seconds before you hear the sound of the explosion. How far away is the explosion?

Homework Equations

d = vt

The Attempt at a Solution

Not really sure how to approach this properly. There is a hint that says: "The difference in the travel times is the time given. "

 

[kev1829]

You should set up a single variable equality using air time and ground time.

 

[moronto]

ah, i got it, thanks