Question

Light travels at 300 000 kilometers per second (km/s), but sound travels much slower at a rate of 0.341 km/s. Karen notices a delay of about
30 seconds between the time she sees an airplane and hears its engine.
How far (in km) is the plane from her when she first sees it?

Answer 1

The sound took 30 sec to reach since the instant she sees that plane, so it would be 30 times 0.341, that makes 10.23km.