Two trains 140 m and 160 m long run at the speed fo 60 k/hr and 40 km/hr respectively in opposite directions on parallel tracks. The time (in seconds) which they take to cross each other, is: Choose the correct answer: A) 7 B) 8.6 C) 10.8 D) 11 E) 12
Sol.   Relative speed = (60 + 40) km/hr = [100 * 5/18] m/sec = [250/9] m/sec.   Distance covered in crossing each other = (140 + 160)= 
<gadget id="calculator">(140 + 160)</gadget>
<output>300</output>
300 m.   Required time= [300 * 9/250] sec = 54/5= 
<gadget id="calculator">54/5</gadget>
<output>54/5 = around 10.8</output>
10.8 ec.   Answer 10.8
<result>C</result>
Two trains 140 m and 160 m long run at the speed fo 60 k/hr and 40 km/hr respectively in opposite directions on parallel tracks. The time (in seconds) which they take to cross each other, is: