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**1. Homework Statement**

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 7.87 km/s and the secondary, or S, wave has a speed of about 4.86 km/s. A seismograph, located some distance away, records the arrival of the P wave and then, 76.8 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?

Pwave = 7.87km/s OR 7870m/s

Swave = 4.86km/s OR 4860m/s

**2. Homework Equations**

I don't think there's an equation specifically for this, if there is, i haven't got it yet

**3. The Attempt at a Solution**

I've figured out that when the pwave reaches the station it takes 76.8s for the swave to get there. So the distance at that point is 373.248km or 373248m. But i can't get the distance that it took before then.

Pwave--------------------------------------------| Station

Swave------------|_______________________| Station

x 373,248m

I tried to make it easier to understand, i can't find the distance "x", i know it traveled some distance before getting to the station i just don't know how to find that.

Someone help.

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