Two trains of equal lengths take 8 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) 22	B) 12	C) 77	D) 10	E) 21
Speed of the first train = 120/8= 
<gadget id="calculator">120/8</gadget>
<output>15</output>
15 m/sec.   Speed of the second train= 120/15= 
<gadget id="calculator">120/15</gadget>
<output>8</output>
8 m/sec.   Relative speed= 15 + 8= 
<gadget id="calculator">15 + 8</gadget>
<output>23</output>
23 m/sec.   Required time= (120 + 120)/23 = 10 sec.   Answer: 10
<result>D</result>
Two trains of equal lengths take 8 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?