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 choice from the following answers:
A) 10
B) 25
C) 12
D) 20
E) 30
Explanation:   Speed of train 1 = 12 m/sec   Speed of train 2 = 8 m/sec   if they travel in opposite direction, relative speed = 12 + 8= 
<gadget id="calculator">12 + 8</gadget>
<output>20</output>
20 m/sec   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 sec   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?