Answer : 3. "32 mts"
Explanation :

Answer: C) 32 mts Explanation: let 'b' be the Length of bridge from cow to the near end of the bridge and 'a' be the distance of the train from the bridge. 'x' be speed of cow => '4x' speed of trainThen the total length of the bridge 2b + 10.(a-2)/4x = b/x=> a-2 = 4b........(1)Now if it had run in opposite direction(a+2b+10-2)/4x = (b+10-2)/x=> a - 2b = 24......(2)Solving (1) and (2)b = 11 , Therefore length of the bridge is 2 x 11 + 10 = 32mts.