At a country music festival, a band is playing at the end of a crowded
1947 m field when one of the players hits a note on the keyboard that has
a frequency of 400 Hz. (HINT-find the wavelength first) How much delay
is there between the time the note is played and the time it is heard in
the last row *

t=4.86s

Explanation:

To find the wavelength you use the following formula:

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:

Now, to calculate the time that sound takes to reach the last row you use:

t: time

d: distance to the last row = 1947m

hence, the time is 4.86s