Question

Manmath rowed distance downstream in 7.5 hour while it took him 10.5 hour to row the same distance upstream to make the two way journey in still water how many hour will it take him

Answer 1

Answer:

Time taken by manmath is 17 hours and 30 minutes

Step-by-step explanation:

Let the speed of manmath in still water be x km/hr

Let the speed of current be y km/hr

Speed in upstream = (x - y) km/hr

Speed in downstream = (x + y) km/hr

Also, distance, speed and time are related as

Distance = Speed × Time

Given that manmath rowed a distance downstream in 7.5 hours

Let the distance rowed be d km

Thus, we get

(x + y)(7.5) = d

7.5x + 7.5y = d ---- (1)

Also, manmanth took 10.5 hours to row the same distance upstream.

Thus, we get

(x - y)(10.5) = d

10.5x - 10.5y = d ----- (2)

Solving (1) and (2), we get

 7.5x + 7.5y = d     × 7

 10.5x - 10.5y = d   × 5

--------------------------------------

  52.5x + 52.5y = 7d

  52.5x - 52.5y = 5d

-----------------------------------

  105x + 0y = 12d

  105x = 12d

   d = 105x/12

   2d = 210x/12

Thus, time taken by manmath = 210/12 = 35/2 hours