Question

The speed of a boat in still water is 15 km/h and the speed of a stream is 5 km/h. Find the
time taken by the boat to cover (i) 40 km upstream (ii) 36 km downstream.
Tad the speed of the boat​

Answer 1

Answer:

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

Then, Speed downstream =(15+x) km/hr

Speed upstream =(15−x) km/hr

Time taken by the boat to go 30km upstream =

15−x

30

hours

time taken by the boat to return 30km downstream =

15+x

30

hours hours

It is given that the boat returns to the same point in 4 hours 30 minutes

Step-by-step explanation:

15−x

30

+

15+x

30

=

2

9

⇒

225−x

2

450+30x+450−30x

=

2

9

⇒

225−x

2

900

=

2

9

⇒225−x

2

=200⇒x

2

=25⇒x=±5

But the speed of the stream can never be negative

Hence, the speed of the stream is 5km/hr