h and r are the height and the radi...
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h and r are the height and the radius of the base of right circular cylinder of constant volume V with minimum total surface area. Then (a) r=/V/26 (b) r = /2 (c)h=21 (d) h=31

JEE/Engineering Exams
Maths
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Surface area of cylinder  S=2πrh+2πr2 dsdr2πrdhdr+2πh+4πr For minimum surface area, dsdr=0 2πrdhdr+2πh+4πr=0 dhdr=-h+2rr    ....1 Volume V=πr2h Since volume is constant 0=2πrh+πr2dhdr dhdr=-2hr    .....2 From 1 and 2 -2hr=-h+2rr 2h=h+2r 2r=h

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