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A boat travel 32 km upstream in 8 hr and 28 km downstream in 4 hr. Find the speed of a boat in still water and the speed of current?1). 4 km/hr and 3 km/hr2). 5.5 km/hr and 1.5 km/hr3). 4 km/hr and 2 km/hr4). 5 km/hr and 2 km/hr |
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Answer» Distance travelled by boat in upstream = 32 km, time taken = 8 hr SPEED of boat in upstream = 32/8 km/hr = 4 km/hr And distance travelled by boat in DOWNSTREAM = 28 km, time taken = 4 hr Speed of boat in downstream = 28/4 = 7 km/hr Now, speed of the boat in still WATER ⇒ 1/2 × {speed of boat in upstream + speed of boat in downstream} ⇒ 1/2 × [4 + 7] = 1/2 × 11 = 5.5 km/hr Speed of the current = 1/2 × {speed of boat in downstream - speed of boat in upstream} ⇒ 1/2 × [7 - 4] = 1.5 km/hr ∴ Speed of the boat in still water is 5.5 km/hr and Speed of the current is 1.5 km/hr |
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