Efundamental frequency of an open organ pipe corresponds to the middle c (261.6 hz on the chromatic musical scale). the third resonance of a closed organ pipe has the same frequency. (assume that the speed of sound in air is 343 m/s.) (a) what is the length of the open pipe

The wavelength of the third resonance of the closed organ pipe is equal to the ratio between the speed of sound and the frequency of the 3rd harmonic:

The relationship between length of a closed pipe and wavelength of the standing waves inside is:

where n is the number of the harmonic. In this case, n=3, so the length of the pipe is

think its the third option