Arithmetic

Time, Speed & Distance

Hard

Viraj swims for $12\frac{1}{2}$ hours while going 24 km down stream and 36 km upstream. But he takes just 12 hours to swim 36 km down steam and 24 km up stream. At what rate is the river flowing ?

1.1 km/hr

2.1 km/hr

3.1 km/hr

4.1 km/hr

✅ Correct Option: 1

Let downstream speed $= d$ , upstream $= u$ . Then $\frac{24}{d}+\frac{36}{u}=12.5$ and $\frac{36}{d}+\frac{24}{u}=12$ . Solving gives $d = \frac{60}{11}$ , $u = \frac{40}{9}$ . River speed $= \frac{d-u}{2} \approx 0.5$ km/hr, which does not match any option cleanly.

Note: The given numerical values in the question do not produce any of the listed options; we have picked the closest numerical match.

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Solution

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CUET General Test Past Year Questions (Topic-Wise)

Viraj swims for $12\frac{1}{2}$ hours while going 24 km down stream and 36 km upstream. But he takes just 12 hours to swim 36 km down steam and 24 km up stream. At what rate is the river flowing ?