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

CBSE Class 12 Sample Paper for 2022 Boards (MCQ Based - for Term 1)
CBSE Class 12 Sample Paper for 2022 Boards (MCQ Based - for Term 1)
Last updated at Dec. 16, 2024 by Teachoo
Transcript
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) = ššš/š š + šššššš/š Differentiating w.r.t v Cā(v) = ššš/š ā šššššš/š^š Putting Cā(v) = 0 0 = 375/4 ā 600000/š£^2 600000/š£^2 = 375/4 600000 Ć4/375 = š£^2 600000 Ć4/375 = š£^2 1600 Ć 4 = š^š 40 Ć 2 = š 80 = š š = 80 km/hr So, the correct answer is (c)