A motar boat travelling upstream met rafts floating downstream. One hour after this the
engine of the boat stopped. It took 30mins to repair it, and during this time the boat freely
floated downstream. When the engine was repaired, the boat travelled downstream with the
same speed relative to the stream as before and overtakes the raft at a distance s=7.5km from
the point where they met before. Determine the speed of the river.
Answers
Speed of the River = 3 km/Hr
Explanation:
Speed of Boat = B km/hr
Speed of river = R km/hr
rafts floating downstream speed = R km/hr
in 1 hr Distance covered by Boat = ( B - R) * 1 km
Distance covered by Raft = R * 1 km ( in opposite direction)
Difference between Both = B - R + R = B km
Distance of boat from meeting point = B - R km
Distance of Raft from meeting point = R km
Next 30 Mins both are moving freely downstream
so Distance between both = B km
Distance of boat from meeting point = B - R - R/2 = B - 3R/2 km
Distance of Raft from meeting point = R + R/2 = 3R/2 km
Let say after that it Tooks T hr to meet them
3R/2 + RT = 7.5 km
Down stream Speed = B + R
Distance covered = Distance between both + Distance covered by Raft during that time
(B + R) T = B + RT
=> BT = B
=> T = 1
3R/2 + R = 7.5
=> 5R = 15
=> R = 3 km/hr
Speed of the River = 3 km/Hr
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