[tex] \small\bf \: let \: the \: distance \: of \: the \: man \: from \: the \: cliff \: be \: x[/tex]
[tex] \small\bf \: thus \: time \: taken \: by \: sound \: to \: hit \: the \: cilff \: and \: return = \frac{2x}{v} = 1[/tex]
[tex] \bf \to \: x = \frac{320}{2} m = 160m[/tex]
[tex] \small \bf \: thus \: the \: distance \: between \: the \: cliffs \: = 160m \times 2 = 320m[/tex]