Two goods trains each 820 m long are running in opposite directions on parallel tracks. Their speeds are 45 km/hr and 30 km/hr respectively. Find the time taken by the slower train to pass the driver of the faster one?  Choose the correct choice from the following: A) 228 B) 27.32 C) 76.6 D) 78.72 E) 21
Relative speed = 45 + 30= 
<gadget id="calculator">45 + 30</gadget>
<output>75</output>
75 km/hr.   75 * 5/18= 125/6 m/sec.   Distance covered = 820 + 820= 
<gadget id="calculator">820 + 820</gadget>
<output>1_640</output>
1640 m.   Required time= 1640 * 6/125= 
<gadget id="calculator">1640 * 6/125</gadget>
<output>1_968/25 = around 78.72</output>
78.72 sec.   Answer:78.72
<result>D</result>
Two goods trains each 820 m long are running in opposite directions on parallel tracks. Their speeds are 45 km/hr and 30 km/hr respectively. Find the time taken by the slower train to pass the driver of the faster one?