Speed of sound in air near room temperature is approximately

At what temperature is the velocity of sound double that of its velocity at $0^{\circ}C$?

For a particular sound wave propagating in air, a path difference between two points is $0.54 \, m$ which is equivalent to a phase difference of $(1.8 \pi)$. If the velocity of the sound wave in air is $330 \, m/s$, the frequency of this wave is: (in $Hz$.)

$A$ hospital uses an ultrasonic scanner to locate tumours in a tissue. What is the wavelength of sound in the tissue in which the speed of sound is $1.7 \; km/s$? The operating frequency of the scanner is $4.2 \; MHz$.

The frequency of a sound wave is $n$ and its velocity is $v$. If the frequency is increased to $4n$,the velocity of the wave will be

$A$ metal rod of $1 \; m$ length is dropped vertically onto a hard metal floor. Using an oscilloscope,it is determined that the impact produces a longitudinal wave of $1.2 \; kHz$ frequency. The speed of sound in the metal rod is: (in $; m/s$)