1.

35 m350 km - 25 Km. 1250 m=​

Answer»

Let spped of WATER is X km/h and speed of stream is y km/h.

Then, speed at UPSTREAM =x-y km/h

Speed at downstream =x+y km/h

Case -1 :

25

x-y

+

35

x+y

=10

⇒

5

x-y

+

7

x+y

=2→(1)

Case-2 :

40

x-y

+

49

x+y

=15→(2)

Let

1

x-y

=a,

1

x+y

=b

So, the equation (1) and (2) becomes,

5a+7b=2→(3)

40a+49b=15→(4)

Now, multiplying (3) with 7 and subtracting it from (4),

⇒40a+49b-35a-49b=15-14

⇒5a=1

⇒a=

1

5

Putting value of a in (3),

⇒5(

1

5

)+7b=2

⇒b=

1

7

∴x-y=5andx+y=7

⇒x-y+x+y=5+7

⇒2x=12⇒x=6

⇒y=7-6=1

∴ Speed of the stream is 1 km/h and speed of BOAT is 6 km/h.


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