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
JEE MAIN 2019, Medium
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$\mathrm{f}_{1}=\mathrm{f}_{0}\left(\frac{340}{340-34}\right) \quad ; \quad \mathrm{f}_{2}=\mathrm{f}_{0}\left(\frac{340}{340-17}\right)$
$\frac{f_{1}}{f_{2}}=\frac{323}{306}=\frac{19}{18}$
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