Two trains of equal lengths take 10 sec and 18 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?	Pick one:
A) 11
B) 9
C) 13
D) 14
E) 12.8
Speed of the first train = 120/10= 
<gadget id="calculator">120/10</gadget>
<output>12</output>
12 m/sec.   Speed of the second train= 120/18 = 6.7 m/sec.   Relative speed = 12 + 6.7= 
<gadget id="calculator">12 + 6.7</gadget>
<output>18.7</output>
18.7 m/sec.   Required time= (120 + 120)/18.7 = 12.8 sec.   Answer: Option 12.8
<result>E</result>
Two trains of equal lengths take 10 sec and 18 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?