Answer:
t=4.86s
Explanation:
To find the wavelength you use the following formula:
[tex]v=\lambda f[/tex]
v: speed of sound = 343m/s
f: frequency = 400Hz
λ: wavelength of the sound
By doing λ the subject of the formula and replacing the values of f and v you obtain:
[tex]\lambda=\frac{v}{f}=\frac{343m/s}{400Hz}=0.85m[/tex]
Now, to calculate the time that sound takes to reach the last row you use:
[tex]t=\frac{d}{v}[/tex]
t: time
d: distance to the last row = 1947m
[tex]t=\frac{1947m}{400Hz}=4.86s[/tex]
hence, the time is 4.86s