Question

3. A boat takes 9 hours to travel a distance upstream and takes 3 hours to travel the same distance
downstream. If the speed of the boat in still water is 4 km/hr, what is the speed of the stream?​

Answer 1

Answer:

2km/hr

Step-by-step explanation:

x-y=d/9 and x+y=d/3

from speed=dist /time

taking d as common

(x-y)9=(x+y))3

subs x=4in eq

y=2km/hr

Answer 2

Upstream = T = 9 hours

Downstream = T = 3 hours

Speed of the boat in still water = 4 km/hr

Let the speed of the stream be = x km/hr

Speed of the boat upstream = ( x - 4 ) km/hr

Speed of the boat downstream = ( x + 4 ) km/

hr

Distance travelled upstream = 9 ( 4 - x ) km

Distance travelled downstream = 3 ( 4 + x )

km

According to the question,

9 ( 4 - x ) = 3 ( 4 + x )

36- 9x = 12 + 3x

-9x - 3x = 12 - 36

- 12x = - 24

x = 24

12

Both cut & the answer is

x = 2 km /hr ( speed of the stream )