Two trains of equal lengths take 10 sec and 8 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? Choices
A) 22  B) 12  C) 9  D) 99  E) 21
Speed of the first train = 120/10= 
<gadget id="calculator">120/10</gadget>
<output>12</output>
12 m/sec.   Speed of the second train= 120/8= 
<gadget id="calculator">120/8</gadget>
<output>15</output>
15 m/sec.   Relative speed= 12 + 15= 
<gadget id="calculator">12 + 15</gadget>
<output>27</output>
27 m/sec.   Required time= (120 + 120)/27 = 9 sec.   Answer: 9
<result>C</result>
Two trains of equal lengths take 10 sec and 8 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?