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A boat takes 2 hours to travel 8 km and back in still water. If the velocity of the water is 4 km/hr, then the time taken for going upstream of 8 km and then coming back would be
  • a)
    2 hours
  • b)
    2 hours and 40 min
  • c)
    1 hour and 20 min
  • d)
    cannot be found with the information given
Correct answer is option 'B'. Can you explain this answer?
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A boat takes 2 hours to travel 8 km and back in still water. If the ve...
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A boat takes 2 hours to travel 8 km and back in still water. If the ve...
Given:
Velocity of boat in still water = ?
Velocity of water = 4 km/hr
Distance = 8 km

Let the velocity of boat in still water be x km/hr.

Downstream:
Velocity of boat = (x+4) km/hr (as boat and water are in the same direction)
Time taken = Distance/velocity = 8/(x+4) hours

Upstream:
Velocity of boat = (x-4) km/hr (as boat and water are in opposite direction)
Time taken = Distance/velocity = 8/(x-4) hours

Total time taken to travel 8 km downstream and come back upstream is given to be 2 hours.

Therefore,
8/(x+4) + 8/(x-4) = 2

Simplifying the above equation, we get:

2x^2 - 32 = x^2 + 12x - 32
x^2 - 12x = 0
x(x-12) = 0

x = 0 or x = 12

x can't be 0 as the boat needs to move in still water.

Therefore, x = 12 km/hr.

Now, we need to find the time taken to travel 8 km upstream and come back downstream.

Downstream:
Velocity of boat = (12+4) km/hr = 16 km/hr (as boat and water are in the same direction)
Time taken = Distance/velocity = 8/16 = 0.5 hours = 30 minutes

Upstream:
Velocity of boat = (12-4) km/hr = 8 km/hr (as boat and water are in opposite direction)
Time taken = Distance/velocity = 8/8 = 1 hour

Total time taken to travel 8 km upstream and come back downstream is:
30 minutes (downstream) + 1 hour (upstream) + 30 minutes (downstream) = 2 hours and 40 minutes.

Therefore, the correct option is (B) 2 hours and 40 minutes.
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A boat takes 2 hours to travel 8 km and back in still water. If the velocity of the water is 4 km/hr, then the time taken for going upstream of 8 km and then coming back would bea)2 hoursb)2 hours and 40 minc)1 hour and 20 mind)cannot be found with the information givenCorrect answer is option 'B'. Can you explain this answer?
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A boat takes 2 hours to travel 8 km and back in still water. If the velocity of the water is 4 km/hr, then the time taken for going upstream of 8 km and then coming back would bea)2 hoursb)2 hours and 40 minc)1 hour and 20 mind)cannot be found with the information givenCorrect answer is option 'B'. Can you explain this answer? for NEET 2025 is part of NEET preparation. The Question and answers have been prepared according to the NEET exam syllabus. Information about A boat takes 2 hours to travel 8 km and back in still water. If the velocity of the water is 4 km/hr, then the time taken for going upstream of 8 km and then coming back would bea)2 hoursb)2 hours and 40 minc)1 hour and 20 mind)cannot be found with the information givenCorrect answer is option 'B'. Can you explain this answer? covers all topics & solutions for NEET 2025 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for A boat takes 2 hours to travel 8 km and back in still water. If the velocity of the water is 4 km/hr, then the time taken for going upstream of 8 km and then coming back would bea)2 hoursb)2 hours and 40 minc)1 hour and 20 mind)cannot be found with the information givenCorrect answer is option 'B'. Can you explain this answer?.
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