When an earthquake occurs...?

Question

When an earthquake occurs, two types of sound waves are generated and travel through the earth. The primary, or P, wave has a speed of about 8.0 km/s and the secondary, or S, wave has a speed of about 4.5 km/s. A seismograph, located some distance away, records the arrival of the P wave and then, 78 s later, records the arrival of the S wave. Assuming that the waves travel in a straight line, how far is the seismograph from the earthquake?

Can you tell me how you did it if you get this? Thanks!

Answer 1

s=(v2-v1)t

The distance traveled is the difference between speeds times the difference in time (t)

s=(8 - 4.5) x 78 = 273km