Two trains running in opposite directions cross a man standing on the platform in 27 seconds and 17 seconds respectively and they cross each other in 20 seconds. The ratio of their speeds is?
Choices:	A) 3/7	B) 3/2	C) 3/5	D) 3/1	E) 3/3
Let the speeds of the two trains be x m/sec and y m/sec respectively. Then, length of the first train = 27 x meters, and length of the second train = 17 y meters. (27 x + 17 y) / (x + y) = 20   ==&gt; 27 x + 17 y = 20 x + 20 y ==&gt; 7 x = 3 y ==&gt; x/y   = 3/7.   3/7nswer: 3/7
<result>A</result>
Two trains running in opposite directions cross a man standing on the platform in 27 seconds and 17 seconds respectively and they cross each other in 20 seconds. The ratio of their speeds is?