An echo-sounder in a fishing boat receives an echo from a shoal of fish 0.45 s after it was sent. If the speed of sound in water is 1500 m/s, how deep is the shoal?

Going through the sums, we can list the given quantities as,

speed v= 1500 m/s

time in which the signal is recieved back after hitting the shoal,

i.e time for going+time for coming back i.e 2t = 0.45 s 

therefore t = 0.225s

To find distance d = ?

Solution – 

velocity, distance and time can be related as

distance =  speed x time 

d = v x t

d = 1500 x 0.225

d = 337.5m

the distance between the shoal and the echo sounder is 337.5m