For the formation of beats,two sound notes must have:

$A$ tuning fork and an air column whose temperature is $51^{\circ} C$ produce $4$ beats in one second,when sounded together. When the temperature of the air column decreases,the number of beats per second decreases. When the temperature is $16^{\circ} C$,only one beat per second is produced. The frequency of the tuning fork is ........... $Hz$.

Two adjacent piano keys are struck simultaneously. The notes emitted by them have frequencies $n_1$ and $n_2$. The number of beats heard per second is

Two sound waves of wavelengths $99 \ cm$ and $100 \ cm$ produce $10$ beats in a time of $t$ seconds. If the speed of sound in air is $330 \ m \ s^{-1}$,then the value of $t$ in seconds is

Two tuning forks $A$ and $B$ are sounded together giving rise to $8$ beats in $2$ s. When fork $A$ is loaded with wax,the beat frequency is reduced to $4$ beats in $2$ s. If the original frequency of tuning fork $B$ is $380$ Hz,then the original frequency of tuning fork $A$ is . . . . . . Hz.

$A$ tuning fork gives $5$ beats with another tuning fork of frequency $100\,Hz.$ When the first tuning fork is loaded with wax,the number of beats remains unchanged. What is the frequency of the first tuning fork in $Hz$?