A 300 m long train crosses a platform in 39 sec while it crosses a signal pole in 20 sec. What is the length of the platform?	Pick:
A) 389 m  B) 350 m  C) 285 m  D) 299 m  E) 219 m
Speed = 300/20= 
<gadget id="calculator">300/20</gadget>
<output>15</output>
15 m/sec.   Let the length of the platform be x meters.   Then, (x + 300)/39= 15   =&gt; x = 285 m.   Answer:285 m
<result>C</result>
A 300 m long train crosses a platform in 39 sec while it crosses a signal pole in 20 sec. What is the length of the platform?