SOLUTION: 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?

Algebra ->  Surface-area -> SOLUTION: 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?      Log On


   

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?
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
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%2Api%2Ar%5E2 + 2%2Api%2Ar%2Ah
Using the given values
2%2Api%2Ar%5E2 + 2%2Api%2Ar%2A1.5 = 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