How deep is the water if it takes a pulse of ultrasound 0.8s to be received back at the boat. the speed of ultrasound is 1600m/s in water

firstly we know how fast the wave is travelling and we know for how long so using our speed equals distance over time equation we can rearange for distance (D= VT).

we can the plug in our speed(V) and our time (T) to get distance = 1600 x 0.8                                     this gives use a distance of 1280 m.

however we have to rememeber that the wave had to go down to the sea floor then back up to the boat so it has travelled two times the depth of the sea.

therefore the depth of the sea is 1280 / 2  = 640m