Let the fundamental frequency of organ pipe be f Case I : f =200 ± 5 = 205 Hz or 195 Hz
Case II : frequency of 2nd harmonic of organ pipe = 2f (as is clear from the second figure) 2 f = 420 ± 10 or f = 210 ± 5 or f = 205 or 215 Hence fundamental frequency of organ pipe = 205 Hz