SSC MTS 5 Aug 2019 Shift 3 Paper

Let the length of train be x
Speed of train = length of train/time
Speed of train = x/60
Length of the bridge = 2x
Speed of train = (length of train + length of bridge) /time
x/60 = (x + 2x) /time
time = 60 × 3 = 180 seconds
∴ Train will take 180 seconds to cross the bridge.