$A$ source of sound is moving towards a stationary observer with $\frac{1}{10}$ of the speed of sound. The ratio of apparent to real frequency is

$A$ source of sound is travelling with a velocity of $40 \, km/h$ towards an observer and emits sound of frequency $2000 \, Hz$. If the velocity of sound is $1220 \, km/h$,what is the apparent frequency heard by the observer in $Hz$?

$A$ man is standing between two trains moving away from and towards him,both with a speed of $4 \, m/s$. If both trains produce a sound of frequency $240 \, Hz$,calculate the number of beats heard by the man. (Speed of sound in air = $320 \, m/s$)

$A$ source of sound and a listener are approaching each other with a speed of $40 \, m/s$. The apparent frequency of the note produced by the source is $400 \, cps$. Then,its true frequency (in $cps$) is (velocity of sound in air $= 360 \, m/s$).

$A$ person is observing two trains,one coming towards him and the other leaving with the same speed $4\, m/s$. If their whistling frequencies are $240\, Hz$ each,then the number of beats per second heard by the person will be: (if the velocity of sound is $320\, m/s$)

$A$ source of sound of frequency $n$ is moving towards a stationary observer with a speed $S$. If the speed of sound in air is $V$ and the frequency heard by the observer is $n_1$,the value of $n_1/n$ is