Posted by Smartypants on .
A solid rod of radius r cm and length l cm has a volume of 50pie cm cube .
(i) show tha the total surface area if the rod is given by
A = 2pieRsquare + 100pie / r

Math 
Damon,
V = pi r^2 L = 50 pi
so L = 50/ r^2
A = 2 pi r^2 (area of ends) + 2 pi r L (area of side)
A = 2 pi r^2 + 2 pi r (50/r^2)
= 2 pi r^2 + 100 pi/r