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 many full
wavelengths are there between the stage and the last row of the crowd?

2270 full wavelengths.

Explanation:

The wavelength of the sound wave (assuming sound speed of  ) is

.

Now, assuming the distance to the last row is 1947m, the number of wavelengths that fit into this distance are

which is 2270 full wavelengths.

Hence, there are 2270 full wavelengths between the stage and the last row of the crowd.

(75°f − 32) × 5/9 = 23.889°c