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Two buses start from a bus terminal with a speed of 20 km/h at interval of 10 minutes. What is the speed of a man coming from the opposite direction towards the bus terminal if he meets the buses at interval of 8 minutes?

A.

5 km/h

B.

C.

4 km/h

D.

3 km/h

Answer with explanation

Answer: Option AExplanation

Let Speed of the man is x kmph.

Distance covered in 10 minutes at 20 kmph = distance covered in 8 minutes at (20 + x) kmph.

Or,

20×1060=860×(20+x)20×1060=860×(20+x)

Or, 200 = 160 + 8x

Or, 8x = 40

Hence, x = 5 kmph.

**Detailed Explanation:**

A _____________M_______________B

A = Bus Terminal.

B = Let meeting point of first bus and the man and this distance is covered by Bus in 10 minutes. I.e. Distance A to be is covered first bus in 10 min. As AB distance can be covered by second bus in 10 minutes as well.

Distance Covered by Bus in 10 min = AB = 2060×102060×10

= 103103 km.

Now, M is the Meeting Point of Second Bus with Man. Man covered distance B to M in 8 minutes.

Now, Relative distance of both Man and Bus will be same as both are traveling in opposite direction of each other. Let Speed of the man = x kmph.

Relative speed = 20 + x

To meet at Point M, bus and Man has covered the distance (AB) in 8 minutes with relative speed. And Same AB distance is covered by bus in 10 minutes. Thus, Distance covered in 8 minutes with relative speed (20 + x) kmph = distance covered by bus in 10 minuted with speed 20 kmph

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