Arithmetic

Time, Speed & Distance

Medium

applied

A person can row a boat at 5 km/hr in still water. If the speed of water current in a river is 1 km/hr, and it takes him 1 hour to row to a place and come back, how far off is the place?

3.6 km

2.4 km

2 km

3.2 km

✅ Correct Option: 2

The boat can row at 5 km/hr in still water. The river current flows at 1 km/hr.

When going downstream (with the current), the speed is:

$5 + 1 = 6$ km/hr

When going upstream (against the current), the speed is:

$5 - 1 = 4$ km/hr

Let the distance to the place be $d$ km.

Time taken going downstream:

$\frac{d}{6}$ hours

Time taken coming back upstream:

$\frac{d}{4}$ hours

Total time for the round trip is 1 hour:

$\frac{d}{6} + \frac{d}{4} = 1$

$\frac{2d}{12} + \frac{3d}{12} = 1$

$\frac{5d}{12} = 1$

$5d = 12$

$d = \frac{12}{5}$

$d = 2.4$ km

Therefore, the place is 2.4 km away.

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2025: 27 May Shift 1

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A person can row a boat at 5 km/hr in still water. If the speed of water current in a river is 1 km/hr, and it takes him 1 hour to row to a place and come back, how far off is the place?

Solution

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