The most economical speed to run the train is:

(a) 18 km/h   (b)5 km/h  (c) 80 km/h        (d) 40 km/h 

 

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Question 48 The most economical speed to run the train is: (a) 18 km/h (b)5 km/h (c) 80 km/h (d) 40 km/h We need to find minimise Cost Now, Cost = C(v) = šŸ‘šŸ•šŸ“/šŸ’ š’— + šŸ”šŸŽšŸŽšŸŽšŸŽšŸŽ/š’— Differentiating w.r.t v C’(v) = šŸ‘šŸ•šŸ“/šŸ’ āˆ’ šŸ”šŸŽšŸŽšŸŽšŸŽšŸŽ/š’—^šŸ Putting C’(v) = 0 0 = 375/4 āˆ’ 600000/š‘£^2 600000/š‘£^2 = 375/4 600000 Ɨ4/375 = š‘£^2 600000 Ɨ4/375 = š‘£^2 1600 Ɨ 4 = š’—^šŸ 40 Ɨ 2 = š’— 80 = š’— š’— = 80 km/hr So, the correct answer is (c)

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Davneet Singh

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 14 years. He provides courses for Maths, Science and Computer Science at Teachoo