A train covers a distance of 10 km in 12 minutes. If its speed is decreased by 5 km/h, what will be the time taken by it to cover the same distance? MCQ with Answer and Explanation

Explanation:
Downstream speed = Speed in still water + Speed of current = 14 + 4 = 18 km/h. Time taken = Distance / Downstream speed = 72 / 18 = 4 hours.

Explanation:
Original speed = 240 / 4 = 60 km/h. New speed = 60 - 10 = 50 km/h. Time for 300 km = 300 / 50 = 6 hours.

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.