Question

(i) Ritu can row downstream 20 km in 2 hours, and upstream
4 km in 2 hours. Find her speed of rowing in still water
and the speed of the current.​

Answer 1

Answer:

Step-by-step explanation:

Speed of the boat = x km/h

Speed of current = y km/h

Speed Downstream = x + y

Speed Upstream = x - y

FOR DOWNSTREAM :-

Distance covered = 20 km

Time taken = 2 hours

Speed Downstream = x + y  

By using the formula, Speed = Distance/Time

We get,

x + y = 20/2

x + y = 10     ............(2)

FOR UPSTREAM :-

Distance covered = 4 km

Time taken = 2 hours

Speed Upstream = x - y

By using the formula, Speed = Distance/Time

We get,

x - y = 4/2

x - y = 2     ............(1)

SOLVING (1) AND (2) :-

x + y = 10

x - y = 2

2x = 12

x = 6

So,

x + y = 10

6 + y = 10

y = 10 - 6

y = 4

SPEED OF BOAT IN STILL WATER = x km/h = 6 km/h

SPEED OF THE CURRENT = y km/h = 4 km/h

hope it helps

 

Answer 2

Let, speed of Ritu in still water be x km/hr

and speed of current be y km/hr

Then speed downstream =(x+y) km/hr

speed upstream =(x−y) km/hr

we know, Time=

Speed

Distance

Then

x+y

20

=2 and

x−y

4

=2

⇒x+y=10 ...(1)

& x−y=2 ...(2)

adding both we get, 2x=12⇒x=6

Thus using (1) y=10−6=4

Hence the speed of Ritu in still water is 6 km/hr and the speed of the current is 4 km/hr.