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

Step-by-step explanation:

Solution :

Let speed in still water = a km/h

Speed of stream = b km/h

Then downstream speed = a + b

Upstream speed = a - b

According to question,

⇒ 20/(a + b) = 2

⇒ a + b = 10 ..... (i)

⇒ 4/(a - b) = 2

⇒ a - b = 2 ..... (ii)

Add (i) and (ii)

⇒ 2a = 12 

⇒ a = 6

From (i), we get

⇒ a + b = 10

⇒ 6 + b = 10

=> b = 4

• a = 6
• b = 4

Ritu's speed in still water = 6km/h

Ritu's speed of current = 4km/h

Answer 2

Answer:

6  km/hr and 4 km/hr

Step-by-step explanation:

Speed in steel water- s

Speed of the current- c

Speed downstream= s+c

Speed upstream= s-c

• (s+c)*2=20 => s+c=10
• (s-c)*2=4 => s-c=2
• 2s=12
• s=6 km/hr
• c=4 km/hr

Rowing speed= 6 km/hr

Speed of current= 4 km/hr