Two card are moving in the same direction with the same speed of ` 30 km h^(-10` at a distance of ` 5km` from each other . A third car moving in the opposite direction meets these two card at an interval of `4` minutes. Find the speed of third car.

Options

A. 45km/h
B. 30km/h
C. 25km/h
D. 40km/h

Answer

a

Explanation

Let speed of the car is u. and it is moving opposite to the buses hence relative speed of approach becomes 30+u. since relative speed is constant hence we can write the time take as follows:
`t=("distance")/("relative speed")=(5)/(30+u)`
Time is given to be 4min, hence we can write the following,
`(4)/(60)=(5)/(30+u)`
`rArr 30+u=75`
`rArr u=45km//h`