Ravi goes to college from his village

Ravi goes to college from his village at the speed of 5km/h and returns at the speed of 4km/h. If he takes 9 hours in all, find the distance (in km) between the village and the college.
रवि अपने गांव से कॉलेज 5km/h की चाल से जाता है और 4 km/h की चाल से वापस आता हैं। यदि उसे कुल मिलाकर 9 घंटे लगते हैं, तो गांव और कॉलेज के बीच की दूरी (km में) ज्ञात कीजिए।

18 20 9 40

Detailed Solution & Logic

Correct Answer:

20

Speed (going) = 5km/h
Speed (returning) = 4 km/h
Let distance $= x$ km
Time going = $ \dfrac{x}{5} $
Time returning = $ \dfrac{x}{4} $
Total time = 9 h
$ \dfrac{x}{5} + \dfrac{x}{4} = 9 $
$ \dfrac{4x + 5x}{20} = 9 $
$ \dfrac{9x}{20} = 9 $
$ x = 20 $
Answer: 20 km

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