Answer:

According to the question, r1 = 1000 km, r2 = 3500 km, r3 = 6400 km and d1 = 1000 km

And we can calculate,

d2 = 3500 – 1000

d2 = 2500 km

d3 = 6400 – 3500

d3 = 2900 km

Expression for the solid distance is given as follows:

2(d1 + d3) = 2(1000 + 2900)

2(d1 + d3) = 2(3900)

The wave takes the following amount of time to produce an earthquake:

= (3900)(2)/8 sec

Now the liquid distance is given by

2d2 = (2)(2500)

Similarly, the time taken by the seismic wave in the liquid part is

= (2)(2500)/5

As a result, total time taken equals the time spent by the wave during the earthquake’s creation plus the time spent by the seismic wave in the liquid part.

$ Time=2\left[ \frac{3900}{8}+\frac{2500}{5} \right]=1975\sec  $

$ Time=32\min 55\sec  $