An engine giving a whistle is moving towards a stationary observer with a speed of $110\, m/s$. What will be the ratio of the frequency of the whistle heard when the engine is approaching and receding from the observer? (Speed of sound $= 330\, m/s$)

Two cars are moving on two perpendicular roads towards a crossing with uniform speeds of $72\; km/hr$ and $36\; km/hr$. If the first car blows a horn of frequency $280\; Hz$,then the frequency of the horn heard by the driver of the second car when the line joining the cars makes a $45^o$ angle with the roads will be .... $Hz$.

$A$ car is moving at a velocity of $17 \ m/s$ towards an approaching bus that blows a horn at a frequency of $640 \ Hz$ on a straight track. The frequency of this horn appears to be $680 \ Hz$ to the car driver. If the velocity of sound in air is $340 \ m/s$, then the velocity of the approaching bus is: (in $m/s$)

$A$ source of sound of frequency $450 \text{ cycles/sec}$ is moving towards a stationary observer with $34 \text{ m/sec}$ speed. If the speed of sound is $340 \text{ m/sec}$,then the apparent frequency will be ..... $\text{cycles/sec}$.

$A$ train,standing at the outer signal of a railway station,blows a whistle of frequency $400\; Hz$ in still air.
$(i)$ What is the frequency of the whistle for a platform observer when the train $(a)$ approaches the platform with a speed of $10\; m s^{-1}$,$(b)$ recedes from the platform with a speed of $10\; m s^{-1}$?
$(ii)$ What is the speed of sound in each case? The speed of sound in still air can be taken as $340\; m s^{-1}$.

$A$ siren emitting sound of frequency $800 \; Hz$ is going away from a static listener with a speed of $30 \; m/s$. The frequency of the sound heard by the listener is... $Hz$ (take velocity of sound as $330 \; m/s$).