rule
V=PI*r squared h
Find the square of h = v/pi * r.
Oil drum surface area S= bottom surface+side surface =π* r square +2PI*r*h
S=PI*r square +2PI*r*V/PI*r square.
The question now becomes r=? S gets the minimum value.
DS/dr= self-help =0
r=？
H= V/PI*r squared =?
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