Question:medium

A man can row a boat at 8 km/h in still water. If the speed of the water current is 2 km/h and it takes him 2 hours to row to a place and come back, how far off (in km) is the place?

Updated On: Jan 16, 2026
  • 7.5 km
  • 6 km
  • 9.5 km
  • 10 km
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The Correct Option is A

Solution and Explanation

Given:

  • Boat speed in still water: 8 km/h
  • Current speed: 2 km/h
  • Total round trip time: 2 hours

Let the distance to the destination be \(d\) km.

Speed downstream (with current):

\[ \text{Speed}_{\text{down}} = 8 + 2 = 10 \text{ km/h} \]

Speed upstream (against current):

\[ \text{Speed}_{\text{up}} = 8 - 2 = 6 \text{ km/h} \]

Time taken:

\[ \text{Time}_{\text{down}} = \frac{d}{10} \text{ hours} \\ \text{Time}_{\text{up}} = \frac{d}{6} \text{ hours} \]

Total time equation:

\[ \frac{d}{10} + \frac{d}{6} = 2 \]

Combine fractions with a common denominator of 30:

\[ \frac{3d}{30} + \frac{5d}{30} = 2 \\ \frac{8d}{30} = 2 \\ 8d = 60 \\ d = \frac{60}{8} = 7.5 \text{ km} \]

The distance is 7.5 km.

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