Question 529881
A cylinder has a height of 1.5 inches and a total surface area of 4pi square inches.
 What is its approximate radius rounded to the nearest hundredth?
:
The surface area of a cylinder is  given by the formula:
S.A. = {{{2*pi*r^2}}} + {{{2*pi*r*h}}}
Using the given values
{{{2*pi*r^2}}} + {{{2*pi*r*1.5}}} = {{{4pi}}}
we can greatly simplify this, divide thru by 2pi, results
r^2 + 1.5r = 2
r^2 + 1.5r - 2 = 0
Using the quadratic formula, where a=1, b=1.5 c=-2
The positive solution .85078, approx radius = .85 inches