At what speed should a source of sound move so that stationary observer finds the apparent frequency equal to half of the original frequency

At what speed should a source of sound move so that observer finds the apparent frequency equal to half of the original frequency ?

The speed at which a source of sound should move so that a stationary observer finds the apparent frequency equal to 11//12 of the original frequency

At what speed should a source of sound move away from a stationary observer so that observer finds the apparent frequency equal to half of the original frequency?

The speed of sound in air is 340 m/s. The speed with which a source of sound should move towards a stationary observer so that the apparent frequency becomes twice of the original

When the source is moving towards the stationary observer, the apparent frequency is given by

What should be the velocity of a sound source moving towards a stationary observer so that apparent frequency is double the actual frequency (Velocity of sound is v )

if the speed of a sound source is equal to the speed fo sound and the source is moving away from the observer, then the ratio of apparent frequency to the original frequency is