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Subject :NSO    Class : Class 9

Earthquakes generate sound waves inside the earth. Unlike a gas, the earth can experience both transverse S and longitudinal P sound waves. Typically the speed of S wave is about 4.0 km s-1, and that of P wave is 8.0 km s-1. A seismograph records P and S waves from an earthquake. The first P wave arrives 4 minutes before the first S wave. Assuming the waves travel in straight line, at what distance does the earthquake occur?

A 960 km
B 640 km
C 1920 km
D 2880 km

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