Question

Men are running in a line along a road with velocity 9 km/hr behind one another at equal distances of 20 m . Cyclists are also riding along the same line in the same direction at 18 km/hr at equal intervals of 30 m. The speed with which an observer must travel along the road in opposite direction so that whenever he meets a runner he also meets a cyclist is

Answer 1

Speed of the runner = 9 km/hr = ( 5/2 ) m/sec

Speed of the cyclist = 18 km/hr = 5 m/sec

Total time = distance travelled / speed = (20 –x)/(5/2) = (30-x)/5

=> x = 10

Time = 4 sec Speed of observer to travel 10 m in 4 sec = 2.5 m/sec

Answer 2

Answer:

Explanation:

Speed of the runner = 9 km/hr = ( 5/2 ) m/sec

Speed of the cyclist = 18 km/hr = 5 m/sec

Total time = distance travelled / speed = (20 –x)/(5/2) = (30-x)/5

=> x = 10

Time = 4 sec Speed of observer to travel 10 m in 4 sec = 2.5 m/sec