Two trains having equal lengths, take 10 seconds and 15 seconds respectively to cross a post. If the length of each train is 120 meters, in what time (in seconds) will they cross each other when traveling in opposite direction? Choose the correct answer.
A) 10	B) 11	C) 12	D) 13	E) 14
speed of train1 = 120/10= 
<gadget id="calculator">120/10</gadget>
<output>12</output>
12 m/s   speed of train2= 120/15= 
<gadget id="calculator">120/15</gadget>
<output>8</output>
8 m/s   if they travel in opposite direction, relative speed= 12+8= 
<gadget id="calculator">12+8</gadget>
<output>20</output>
20 m/s   distance covered= 120+120= 
<gadget id="calculator">120+120</gadget>
<output>240</output>
240 m   time= distance/speed = 240/20= 
<gadget id="calculator">240/20</gadget>
<output>12</output>
12 s   Answer is 12.
<result>C</result>
Two trains having equal lengths, take 10 seconds and 15 seconds respectively to cross a post. If the length of each train is 120 meters, in what time (in seconds) will they cross each other when traveling in opposite direction?