Question

A person rowing at a speed of 5km/h in still water, takes thrice as much time in going 40 km upstream as in going 40 km downstream. Find the speed of the stream.

Answer 1

 speed of boat   = 5 km/hr
lets speed of stream = x km/hr
 so now while going upstream  speed of guy = 5-x
and while going downstream = 5+ x

A/Q   40/5-x = 3 * 40/ 5+x

   ⇒  5+x = 3 (5-x )  ⇒ 5+x = 15 - 3x ⇒ 4x = 10 = x = 5/2 km/hr

hope this helps

Answer 2

Step-by-step explanation:

speed of boat   = 5 km/hr

lets speed of stream = x km/hr

 so now while going upstream  speed of guy = 5-x

and while going downstream = 5+ x

A/Q   40/5-x = 3 * 40/ 5+x

  ⇒  5+x = 3 (5-x )  ⇒ 5+x = 15 - 3x ⇒ 4x = 10 = x = 5/2 km/hr

hope this helps