A boat goes 150 km upstream in 30 hours and a distance of 217 km downstream in 31 hours. Find the speed of the boat in still water. (in kmph)

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  1. 2
  2. 6
  3. 8
  4. 4

Answer (Detailed Solution Below)

Option 2 : 6
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UP Police SI (दरोगा) Official PYP (Held On: 2 Dec 2021 Shift 1)
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Detailed Solution

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Given:

Upstream Distance = 150 km

Upstream Time = 30 hours

Downstream Distance = 217 km

Downstream Time = 31 hours

Formula used:

Speed of Boat in Still Water = (Downstream Speed + Upstream Speed) / 2

Downstream Speed = Distance / Time

Upstream Speed = Distance / Time

Calculation:

Upstream Speed = 150 / 30

⇒ Upstream Speed = 5 km/h

Downstream Speed = 217 / 31

⇒ Downstream Speed = 7 km/h

Speed of Boat in Still Water = (7 + 5) / 2

⇒ Speed of Boat in Still Water = 12 / 2

⇒ Speed of Boat in Still Water = 6 km/h

∴ The correct answer is option 2.

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