A siren placed at a railway platform is emitting sound of frequency `5 kHz`. A passenger sitting in a moving train `A` records a frequency of `5.5kHz` while the train approaches the siren. During his return journey in a different train `B` he records a frequency of `6.0 kHz` while approaching the same siren. the ratio the velocity of train `B` to that of train `A` is

Options

A. 242/252
B. 2
C. 4
D. 6

Answer

B

Explanation

`(V_A+V)/(V)=5.5/5, (V_B+V)/(V)=6/5`
Solve to get `(V_B)/(V_A)=2`