Question

speed of a boat in still water is 15 km per hour it goes 30 km upstream and return back at the same point in 4hours 30minute.find the speed of stream​

Answer 1

Speed of water = 15km/hr

Distance travelled upstream and downstream = 30 km

Let, speed of stream be x km/hr

So, time taken to travel 30km upstream =

30/15-x

and, time taken to travel 30km

downstream = 30/15+x

Time taken to travel 30km upstream and

30km downstream = 4 hour 30 min or 9/2 hours

So, the equation formed will be

30/15-x + 30/15+x = 9/2

=> 30(1/15-x + 1/15+x) = 9/2

=> 1/15-x + 1/15+x = 9/2*30 = 3/20

=> (15+x+15-x)/225 - x2 = 3/20

=> 30/225-x2 = 3/20

=> 225-x2 = 30*20/3

=> 225-x2 = 200

=> x2 = 225-200

=> x2 = 25

=> x = 5

But, x = speed of stream

So, speed of the stream = 5 km/hr

Hope this helps!!

Answer 2

hope u can solve from here.. !!!