A train passes a station platform in 21 seconds and a man standing on the platform in 15 seconds. If the speed of the train is 54 km/hr, what is the length of the platform? Choose the correct choice from the following choices
A) 299	B) 277	C) 90	D) 88	E) 112
Speed = [54 * 5/18] m/sec = 15 m/sec.   Length of the train = (15 * 15)= 
<gadget id="calculator">(15 * 15)</gadget>
<output>225</output>
225 m.   Let the length of the platform be x meters.   Then, x + 225 / 21= 15   x + 225 = 315   x = 90 m.   Answer:90
<result>C</result>
A train passes a station platform in 21 seconds and a man standing on the platform in 15 seconds. If the speed of the train is 54 km/hr, what is the length of the platform?