A train moves towards a stationary observer with speed $34\, m/s$. The train sounds a whistle and its frequency registered by the observer is $f_1$. If the speed of the train is reduced to $17\, m/s$, the frequency registered is $f_2$. If speed of sound is $340\, m/s$, then the ratio $f_1/f_2$ is
  • A$18/17$
  • B$19/18$
  • C$20/19$
  • D$21/20$
JEE MAIN 2019, Medium
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