A train passes a static observer in 6 seconds and a platform 160 meters long in 14 seconds. Find the length of the train. MCQ with Answer and Explanation

Explanation:
Let original speed be s. 360/s - 360/(s+10) = 3 => 120/s - 120/(s+10) = 1 => 120(10) = s(s+10) => 1200 = s(s+10). Solving s^2 + 10s - 1200 = 0 gives (s - 30)(s + 40) = 0. Since speed is positive, s = 30 km/h.

Explanation:
Downstream speed = 8 + 2 = 10 km/h. Upstream speed = 8 - 2 = 6 km/h. Let distance be d. d / 10 + d / 6 = 3.2 => 16d / 60 = 3.2 => 16d = 192 => d = 12 km.

Explanation:
Distance = Speed * Time = 300 * 4 = 1200 km. New time = 3 hours 20 minutes = 10/3 hours. New required speed = Distance / New time = 1200 / (10/3) = 1200 * 3 / 10 = 360 km/h.