A ship travels downstream from point (A) to point (B) in two hours and upstream in three hours. Then the time taken by log wood to cover the distance from (A) to (B) is .

Options

A. ` 5 h`
B. `9 h`
C. ` 12 h`
D. ` 1 h`

Answer

C

Explanation

Let ` v-s, v_w` =velocity of ship of ship and tiver water w.r.t. grond,
` S=distance between two points ` A` and ` B` log of wood will move with the velocity of river water.
As per question , ` v_s +v_w = S//2` …(i)
` Subtracting (ii) from (i), we have
` 2 v_w = S/2 - S/3 = S/6 `o r ` v_w= S/ (12)`
:. ` time taken by log of wood,
` t= S/v_w = S/(S//12 ) = 12 H`.