drop q \(10 \% \Rightarrow\) heard frequemy was \(90 \%\) of original so if orisinal \(=\nu\) then apparent \(=0.9 \nu\) usins \(\nu^{\prime}=\nu\left(\frac{v}{v+v s}\right) \quad\); vs \(=\frac{\text { speed of }}{\text { car. }}\) put \(\nu^{\prime}=0.9 v\)

we qet \(0.9=\frac{v}{v+u s} \Rightarrow 0.9 v+0.9 v s=v\)

or \(\quad 0.9 v_s=0.1 V \Rightarrow v_s=\frac{V}{9}\)

put \(v=330 m / s \quad U_s=\frac{330}{9}=36.7 m / s\)