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
(More Questions for each concept available in Login)
Question : 1

The current of a stream runs at 1 km/h. A motorboat goes 35 km upstream and back again at the starting point in 12 h. What is the speed of motorboat in still water ?

Right Option : C
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Question : 2

At   his  usual rowing speed. Kapil can travel 12 miles downstream in a certain river in 6 h less than he takes to travel the same distance upstream. But, if he could double his usual rowing speed for his 24 miles round trip, the downstream 12 miles would then take only 1 h less than the upstream 12 miles. What is the speed of the current ?

Right Option : A
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Explanation
Question : 3

The speed of a motorboat is 30 km/h. It starts from Mumbai at 6 am and reaches Goa at 8 am. Same day, it  starts from Goa at 12 pm and reaches Mumbai at 4 pm. Find the speed of stream.

Right Option : C
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Explanation
 
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