A man rows 10 km/h in still water. If the river current tracks at 2 km/h, it takes him 2.5 hours to row to a point and back. How far is the point? MCQ with Answer and Explanation

Explanation:
Time taken to cross the bridge alone = 12 - 7 = 5 seconds. Speed of train = 110 / 5 = 22 m/s. Length of train = Speed * Time to cross sign post = 22 * 7 = 154 meters.

Explanation:
Upstream speed = 30 / 5 = 6 km/h. Downstream speed = 50 / 5 = 10 km/h. Speed of current stream = (Downstream speed - Upstream speed) / 2 = (10 - 6) / 2 = 2 km/h.

Explanation:
Let original speed be s. 400 / (s - 10) - 400 / s = 2 => 200 / (s - 10) - 200 / s = 1 => 2000 = s(s - 10). Solving s^2 - 10s - 2000 = 0 yields (s - 50)(s + 40) = 0. Original speed = 50 km/h.