Person stood between two mountains he hear two echo the first after 2 second, and the second after 2 second from the first echo
Calculate the distance between two mountains when velocity of sound in air equal 340m/s

distance between person and first mountain = Vxt1/2 = 340x2/2 = 340m

distance between person and second mountain = Vxt2/2 = 340x4/2 = 680m

distance between 2 mountains = 340 + 680 = 1020 m