Two trains of equal lengths take 10 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 choice from the following options.
A) 8  B) 10  C) 12  D) 11  E) 15
Speed = 120/10= 
<gadget id="calculator">120/10</gadget>
<output>12</output>
12 m/sec   speed of the second train= 120/5 = 8 m/sec   relative speed = 12+8= 
<gadget id="calculator">12+8</gadget>
<output>20</output>
20 m/sec   Req time= 120+120/20 = 12 sec   ANSWER 12
<result>C</result>
Two trains of equal lengths take 10 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?