An observer moves towards a stationary source of sound, with a velocity one-fifth of the velocity of sound. What is the percentage increase in the apparent frequency?

Explanation

`v_(0)=-v/5, v_(5)=0`
Apparent freq.`v.=((v-v_(0))/(v-v_(5)))v`
`= ((v-v/5)/(v-0))v=6/5v=1.2v
`%` change`= (Deltav)/v**100=(1.2v-v)/v**100=20%`