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Rahul can row 25 km upstream in 5 hour. If the speed of Rahul in still water is 6km/hr. Find the distance he can row downstream in 20 hour.1. 120 km2. 140 km3. 160 km4. 158 km |
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Answer» Correct Answer - Option 2 : 140 km Given Speed of Rahul in still water (u) = 6 km/hr Rahul rows 25 km upstream in 5 hours Formula used The speed of a boat in still water is u km/hr The speed of the stream is v km/hr, Speed downstream = (u + v) km/hr. Speed upstream = (u - v) km/hr. Calculation Speed of water (v) = km/hr ⇒ Speed in still water (u) = 6 km/hr ⇒ Upstream speed = 25/5 km/hr ⇒ 5 km/hr Speed of Stream = (6 – 5) km/hr ⇒ 1 km/hr Downstream speed = (6 + 1) km/hr ⇒ 7 km/hr Distance travelled in 20 hour downstream ⇒ 7 × 20 = 140 km ∴ The required distance covered is 140 km. |
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