Here, both cars are moving towards each other, hence one car is like an observer and another car is like a source . ∴‌‌vs=50m∕s⇒v0=−50m∕s Frequency of horn blown by the source car, v=250‌Hz According to Doppler's effect, frequency heard by another car v′ is given as v′=‌
v−v0
v−v3
×v=‌
350−(−50)
350−50
×250 ‌∴(v=‌ speed of sound ‌=350m∕s) ‌‌‌‌‌=‌