Question

A BOAT WHOSE SPEED IN 15 KM/HR IN STILL WATER GOES 30 KM DOWNSTREAM AND COMES BACK IN A TOTAL OF 4 HOURS 30 MINUTES. THE SPED OF THE STREAM (INKM/HR) IS

Answer 1

The answer is 5km/hr
This means that
The speed of the stream is 5 km/hr.

Please refer the above photograph for the used process.
Hope this will be helping you!


The question required the following concepts :-
1) Linear equation in one variable

2) Distance =speed X time
So,
Time = Distance /speed

3) upstream speed=(y-x)
Downstream speed= (y+x)
Where, y is speed of boat in still water and x is the speed of the stream.

Using this concept only the answer can be derived.
For detailed explain
Please refer the above photograph...

Thanks!

Answer 2

Hey there!

Let speed of stream = x km/h

∴ Downstream speed = (15+x) km/h

∴ Upstream speed = (15-x) km/h

∴ 30/(15+x) + 30/(15-x) = 4 1/2

→ 900/225-x² = 9/2

→ 9x² = 225

→ x² = 25

→ x = 5

∴ Speed of stream = 5 km/h

Hope it Helps You!