Question

Speed of a boat in still water is 15km/h .It goes 30 km upstream and returns back at the same point in 4 hours 30 minutes . Find the speed of stream. ​

Answer 1

Step-by-step explanation:

hope it helps you

Given :

Speed of boat in still water =15 km/hr

Let x be speed of the stream in km/hr

Speed of the boat upstream =15−x

Speed of the boat down stream =15+x

Time taken for upstream T

1

=

15−x

30

Time taken for downstream T

2

=

15+x

30

Given, T

1

+T

2

=

2

9

=

15−x

30

+

15+x

30

=

2

9

=30(

15−x

1

+

15+x

1

)=

2

9

=30(

(15−x)(15+x)

15+x÷15−x

)=

2

9

=

225−x

2

30×30

=

2

9

=

225−x

2

100

=

2

1

⇒225−x

2

=200

⇒x

2

=25

⇒x=5 ....(∵x is +ve)

⇒x=5 km/hr

Speed of the stream =5 km/hr.

Answer 2

$\huge \bold \red{answer}$

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 30 KM UPSTREAM= 30/ 15 - x

AND, TIME TAKEN TO TRAVEL 30KM DOWNSTREAM = 30/ 15 + x

TIME TAKEN TO TRAVEL 30 KM UPSTREAM AND 30KM DOWNSTREAM= 4 HOUR 30 MINUTES 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

=1/5-x +1/15+x = 9/2 30= 3/20

=30/225- x2 = 3/20

=225- x2 = 200

=x2 = 225 - 200

=x2 = 25

=x2 = 5

BUT, x = SPEED OF STREAM

SO, SPEED OF THE STREAM= 5KM /HR

HOPE IT'S HELP UH ✌️✌️