A man can row 9 km/h in still water. If the river is running at 4 km/h, it takes 8 hours more in upstream than to go downstream for the same distance. How far is the place?

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Question

This question was previously asked in

SSC Selection Post 2024 (Matriculation Level) Official Paper (Held On: 24 Jun, 2024 Shift 1)

Answer 1

Given:

Man's rowing speed in still water = 9 km/h

River speed = 4 km/h

Time difference between upstream and downstream = 8 hours

Formula used:

Speed downstream = (rowing speed + river speed)

Speed upstream = (rowing speed - river speed)

Time = Distance / Speed

Calculations:

Let the distance be D km.

Speed downstream = 9 + 4 = 13 km/h

Speed upstream = 9 - 4 = 5 km/h

Time downstream = \(\frac{D}{13}\ hours\)

Time upstream = \( \frac{D}{5}\ hours\)

Given that time upstream is 8 hours more than time downstream:

⇒ \(\frac{D}{5} - \frac{D}{13} \) = 8

⇒ \(\frac{13D - 5D}{65}\) = 8

⇒ \(\frac{8D}{65} = 8\)

⇒ D = 65 km

∴ The correct answer is option 1 (65 km).

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