57. assignment (speed of sound)

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 374 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?

N=

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