A man sitting in a train which is travelling at 64 kmph observes that a goods train travelling in a opposite direction, takes 18seconds to pass him. If the goods train is 420 m long, find its speed. Choose the correct choice from the following options.
A) 32  B) 15  C) 18  D) 20  E) 25
Relative speed = (420/18)m/s = (420/18)*(18/5)= 
<gadget id="calculator">(420/18)*(18/5)</gadget>
<output>84</output>
84 kmph   speed of goods train= 84-64= 
<gadget id="calculator">84-64</gadget>
<output>20</output>
20 kmph   Answer is 20
<result>D</result>
A man sitting in a train which is travelling at 64 kmph observes that a goods train travelling in a opposite direction, takes 18seconds to pass him. If the goods train is 420 m long, find its speed.