Sound waves transfer

Two monoatomic ideal gases '$1$' and '$2$' of molecular masses $m_1$ and $m_2$ respectively are enclosed in separate containers kept at the same temperature. The ratio of the speed of sound in gas '$1$' to that in gas '$2$' is

$A$ man sets his watch by the sound of a siren placed at a distance of $1 \,km$ away. If the velocity of sound is $330 \,m/s$,what is the status of his watch?

The velocity of sound measured at a given temperature in oxygen and hydrogen is in the ratio of:

$A$ 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 velocity of sound is $v_s$ in air. If the density of air is increased to $4$ times,then the new velocity of sound will be