A locomotive 180 meters long crosses a modern bridge in 30 seconds. If it takes 12 seconds to pass a single post light, find the length of the bridge. MCQ with Answer and Explanation
Explanation:
Let original speed be s. 360 / (s - 10) - 360 / s = 2 => 180 / (s - 10) - 180 / s = 1 => 180(10) = s(s - 10) => 1800 = s(s - 10). Solving s^2 - 10s - 1800 = 0 gives (s - 45)(s + 40) = 0. Since speed is positive, s = 45 km/h.
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