Two trains of equal lengths take 10 seconds and 15 seconds respectively to cross a telegraph post. If the length of each train be 120 metres, in what time (in seconds) will they cross each other travelling in opposite direction? Choose the correct option:
A) 10	B) 12	C) 14	D) 15	E) 20
Speed of the first train =(120/10) m/sec = 12 m/sec   Speed of the second train =(120/15) m/sec = 8 m/sec   Relative speed = (12 + 8)= 
<gadget id="calculator">(12 + 8)</gadget>
<output>20</output>
20 m/sec.   Required time= (120+120)/20= 
<gadget id="calculator">(120+120)/20</gadget>
<output>12</output>
12 sec   answer :12
<result>B</result>
Two trains of equal lengths take 10 seconds and 15 seconds respectively to cross a telegraph post. If the length of each train be 120 metres, in what time (in seconds) will they cross each other travelling in opposite direction?