Two cars start towards each other at the same time. The distance between the cars is 3000 km. One travels at 60 km/hr and another at 90 km/hr. A bird starts with one of the cars and flies at 400 km/hr towards the other one. When it gets to the other car, it turns and flies back towards the first and continues this to and fro flying when the cars are moving towards each other. Distance travelled by the bird before the cars pass each other is:
Time taken for 2 cars to meet each other = distance travelled / relative speed of cars
T= 3000(90+60)= 20 hours. The bird is travelling till the cars pass each other. The time of travel will be the time taken by the cars to pass each other.
Distance travelLed by bird = speed of bird × time in air = 400×20 = 8000 km