Anwar rows 49.5 kmph in still water. If the river is running at 16.5 kmph, it takes him 90 minutes to row to a place and back. How far is the place? (In km)

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UP Police SI (दरोगा) Official PYP (Held On: 15 Nov 2021 Shift 3)

Answer 1

Given:

Speed of the boat = 49.5 kmph

Speed of the stream = 16.5 kmph

Time = 90 min. = 1.5 hr

Formula used:

Time = Distance / Speed

Calculation:

Downstream speed = 49.5 + 16.5 = 66 km/h

Upstream speed = 49.5 - 16.5 = 33 km/h

Let the distance be "d"

⇒ \(\frac {d}{66} + \frac {d}{33} = 1.5\)

⇒ \(\frac {d + 2d}{66} = 1.5\)

⇒ 3d = 1.5 × 66

⇒ d = 0.5 × 66

⇒ d = 33

∴ The place is 33 km far.

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