A train passes a station platform in 50 sec and a man standing on the platform in 20 sec. If the speed of the train is 72 km/hr. What is the length of the platform?  Choose the most appropriate option.
A) 550  B) 400  C) 700  D) 600  E) 850
Speed = 72 * 5/18= 
<gadget id="calculator">72 * 5/18</gadget>
<output>20</output>
20 m/sec.   Length of the train= 20 * 20= 
<gadget id="calculator">20 * 20</gadget>
<output>400</output>
400 m.   Let the length of the platform be x m . Then,   (x + 400)/50= 20 =&gt; x = 600 m.   Answer: 600
<result>D</result>
A train passes a station platform in 50 sec and a man standing on the platform in 20 sec. If the speed of the train is 72 km/hr. What is the length of the platform?