Two trains of equal lengths take 9 sec and 15 sec respectively to cross a telegraph post. If the length of each train be 120 m, in what time will they cross other travelling in opposite direction? Choose the correct answer:  A) 10  B) 11.3  C) 13  D) 14  E) 15
Speed of the first train = 120/9 = 13.3 m/sec.   Speed of the second train = 120/15= 
<gadget id="calculator">120/15</gadget>
<output>8</output>
8 m/sec.   Relative speed= 13.3 + 8= 
<gadget id="calculator">13.3 + 8</gadget>
<output>21.3</output>
21.3 m/sec.   Required time= (120 + 120)/21.3 = 11.3 sec.   Answer: Option 11.3
<result>B</result>
Two trains of equal lengths take 9 sec and 15 sec respectively to cross a telegraph post. If the length of each train be 120 m, in what time will they cross other travelling in opposite direction?