Physics, asked by sarveshbaghl7259, 1 year ago

A rows a boat 100km in 20 hours downstream and 72km in upstream in 18 hours. Find the speed of the boat in still water?

Answers

Answered by ferozemulani
0

Explanation:

downstream speed = 100/20 = 5 km/hr

upstream speed = 72/18 = 4 km/hr

speed of boat in still water = 1/2*(5+4)

= 4.5 km/hr

Answered by sonuvuce
0

Answer:

The speed of the boat in still water us 4.5 km/h

Explanation:

Let the speed of the boat in still water is u km/h

and the speed of the river is v km/h

Then,

The speed of the boat downstream = u+v

Speed of the boat upstream = u-v

using Time = Distance/Speed

Time taken downstream = Distance/Downstrem Speed

or, 20 = 100/(u+v)

⇒ u+v = 100/20

⇒ u+v = 5        .................... (1)

Time taken upstream = Distance/Upstrem Speed

or, 18 = 72/(u-v)

⇒ u-v = 72/18

⇒ u-v = 4        .................... (2)

Adding eq (1) and eq (2) we get

2u = 9

or, u = 9/2 = 4.5

Therefore, the speed of the boat in still water us 4.5 km/h

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