Question

A bus takes 10 seconds to pass a standing man and 28 seconds to pass a traffic light, which is 405 meters long. Determine the time it takes for the bus to pass a boy running towards it at a speed of 9 km/h.

A 20 sec Correct Answer Incorrect Answer
B 9 sec Correct Answer Incorrect Answer
C 15 sec Correct Answer Incorrect Answer
D 25 sec Correct Answer Incorrect Answer
E none of these Correct Answer Incorrect Answer

Solution

ATQ, Let the length of the bus be 'x' meters. So according to question:  x/10 = (x + 405) /28 28x = 10x + 4050 18x = 4050, x = 225 So, the length of the bus = 225 meters Speed of the bus = 225/10 = 22.5 m/s Speed of the boy = 9 X 5/18 = 2.5 m/s Relative speed of the bus = 22.5 + 2.5 = 25 m/s So, the time taken by the bus to cross the boy = 225/25 = 9 seconds

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