A mirror faces a cliff located some distance away Mounted on

A mirror faces a cliff located some distance away. Mounted on the cliff is a second mirror, directly opposite the first mirror and facing toward it. A gun is fired very close to the first mirror. The speed of sound is 343 m/s. How many times does the flash of the gunshot travel the round-trip distance between the mirrors before the echo of the gunshot is heard

Solution

lets assume that echo is heard after t time. distance covered:
by light = 3*10^8 * t
by sound = 343*t

So, number of trips = 3*10^8/343 = 8.75*10^5