A boy standing idle sounds a whistle to his friend at a distance of 1200 m moving away from him in a speeding car at 108 kms /hr. Find the duration after which his friend is going to hear him. (Speed of sound = 330m/sec).  Pick one:
A) 3.6 secs B) 4.00 secs C) 40 secs D) 45 secs E) none of these

Rationale: if friend hears sound after t secs , then 330 * t = 1200 + ( 108 * 5 / 18 ) * t 300 t = 1200 t = 4 secs answer : b
Answer: B