A ship can row at a speed of 7 km/hr in still water while the speed of stream is 2 km/hr. Ship rowing upstream from point A to point B, after travelling to point k which is midpoint of A and B, ship failed to work. The ship retuned along the stream and reached the point A again. In this process ship takes 6 hrs more time than it takes in reaching to point B. 60% of the total distance is:?

Option 4 : 24 km

Given,

Speed of ship in still water = 7 km/hr

Speed of stream = 2 km/hr

Formula:

Speed = Distance/Time

If speed of boat and stream be x and y km/hr respectively, then

Upstream speed = (x + y) km/hr

Downstream speed = (x – y) km/hr

Calculation:

Upstream speed = (7 – 2) = 5 km/hr

Let distance between A and B be 2d km/hr

If k is midpoint between A and B, then distance of Ak = kB = d km

According to the question

d/5 + d/2 – 2d/5 = 6

⇒ (2d + 5d – 4d)/10 = 6

⇒ 3d = 6 × 10

⇒ d = 60/3

⇒ d = 20 km

Total distance is = 2 × 20 = 40 km

∴ 60% of the total distance = 60 × (40/100) = 24 km