Question

what is the minimum size of room to get echo if the velocity of a sound is 320m/sec

Answer 1

approximately about 20 metres

Answer 2

Let the distance be x ;

Minimum time required to hear echo = 0.1 sec
Speed = 320m/sec
Distance = 2x

Speed = distance/Time
320 = 2x/0.1
x = 32/2
x = 16 m

Hence the minimum size of the room should be 16m to hear a clear echo.
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