A train is moving on a straight track with speed $20ms^{-1}$. It is blowing its Whistle at the frequency of 1000 Hz. The percentage change in the frequency heard by a person standing near the track as the train passes him is (speed of sound =$320\;ms^{-1})$ close to :

Question

$\begin{array}{1 1} 18 \% \\ 24\% \\ 6\% \\ 12\% \end{array}$