Solving Statement For Upstream And Downstream


 
 
Concept Explanation
 

Solving Statement For Upstream And Downstream

Solving Statements For Upstream and Downstream: In these type of situations, while calculating upstream speed we subtract the speed of river from the speed of boat because the river is pushing the boat downwards even when the boat is moving upwards. Whereas when the boat is moving downstream the speed is calculated by adding the speed of river to the speed of boat.

Example: A boat goes downstream from one point to another in 9 hours. It covers the same distance upstream in 10 hours. If the speed of the stream is 1 km/hr. Calculate the speed of boat in still water.

Solution:     Let the speed of boat in still water be x km/hr

                    Speed of stream  = 1 km/hr

                    Speed upstream = x-1 km/hr

                    Speed Downstream = x + 1 km/hr

                    large speed= frac{distance}{time}

large distance= speed; X ;time

Distance upstream = (x-1) X 10 = 10x - 10 Km

Distance Downstream = (x+1) X 9 = 9x + 9 Km

According to the question the distance is the same

                          10x-10 = 9x + 9

                          10x - 9x = 9+ 10

                                    x = 19 km/hr

So the speed of boat in still watre = 19 km/hr.

Sample Questions
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Question : 1

A boat covers 24 km upstream and 36 km downstream in 6 hr, while it covers 36 km upstream and 24 km downstream in 6frac{1}{2} hrs. The velocity of the current is :

Right Option : C
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Question : 2

The ship left the harbor and is travelling 60 kilometers downstream. Then it continues on the tributary river (upstream) 20 kilometers. Travel took 77 hours to finish. River speed is 11 km/h. Calculate the speed of a ship.

Right Option : B
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Question : 3

A streamer goes downstream from one port to another in 4 h. It covers the same distance upstream in 5 h. If the speed of the stream is 2 km/h, find the distance between the two ports.

Right Option : D
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Explanation
 
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