A boat covers 35 km downstream in 2 h and covers the same distance upstream in 7 h. Find the speed (in km/h) of the boat in still water.

A boat covers 35 km downstream in 2 h and covers the same distance upstream in 7 h. Find the speed (in km/h) of the boat in still water.
एक नाव धारा के अनुकूल 35 km की दूरी 2 घंटे में तप करती है और धारा के प्रतिकूल समान द्वरी 7 घंटे में तय करती है। शांत जल में नाव की चाल (km/h में) ज्ञात कीजिए।

11.25 28.75 18.25 10.55

Detailed Solution & Logic

Correct Answer:

11.25

Let the speed of the boat in still water be b km/h and the speed of the stream be s km/h.
Downstream speed:
$\frac{35}{2}=17.5$ km/h
Upstream speed:
$\frac{35}{7}=5$ km/h
Speed of the boat in still water:
$\frac{17.5+5}{2}=\frac{22.5}{2}=11.25$ km/h
Answer: 11.25 km/h ✅

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