the speed of the river current is 5 km per hour and actual speed of a boat in still water is 8 km per hour. what distance will the boat cover in 2 hours 20 minutes against the current in the river?
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Let the speed of boat in still water be x km/h
Now
In Upstream, we know that
Speed of Boat = Speed of boat in still water-speed of river current
- Speed of boat in upstream = x - 5
Distance in upstream = 8 km .. Time taken in am = 8 / (x - 5)
[Time = distance/speed] --- (i)
In Downstream
Speed of boat = Speed of boat in still water + speed of river current
- Speed of boat in downstream = x + 5
Distance = 12 km
:: Time taken in downstream = 12/(x + 5) -- - (ii)
According to question
Time taken in upstream = time taken in
downstream
...Eq ( i ) = Eq (ii)
8/(x - 5) = 12/(x + 5)
8(x + 5) = 12(x - 5)
8x + 40 = 12x - 60
4x = 100
x = 25
:: Speed of boat in still water is 25km/h
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