The relationship between distance, time and velocity is:
[tex]v=\frac{d}{t}[/tex]The question ask us for the time, we can solve for t:
[tex]v=\frac{d}{t}\Rightarrow t=\frac{d}{v}[/tex]To find the time that it will take the sound wave travelling at 350 m/s to reach the school at 490m is the distance divided the velocity:
[tex]\begin{gathered} t=\frac{490m}{350\frac{m}{s}} \\ \end{gathered}[/tex][tex]t=1.4s[/tex]The answer is 1.4s
