Question

.. A river flows with a speed of 4 km/hr and a boat sails at the speed of 12 km/hr in still
water. If the boat takes 2 hours to cover some distance, moving downstream then how
much time it will require to cover the same distance moving upstream?
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Answer 1

Answer:

time taken to travel upstream : time taken to travel downstream  = 2 : 1

speed upstream : speed downstream  = 1 : 2  (as speed is inversely proportional to time when distance is constant)

Let speed upstream= x  and speed downstream = 2x

Rate of the stream = (2x-x)/2 =x/2

x/2 is given as 1 km/hr

=> x = 2km/hr

Step-by-step explanation:

Answer 2

Step-by-step explanation:

solution:

4km 2hours

12km x

= 4km × x and 12 × 2hours

= 4x = 24

Now

4x = 24 ÷ 2

= 6hrs

Therefore Answer is = 6hrs