SOLUTION: Please help me with this question, I am having trouble finding the answer: A = 2πr^2 + 2πrh = surface area of steel cylinder Question: Find the required radius of

Algebra.Com
Question 1066747: Please help me with this question, I am having trouble finding the answer:
A = 2πr^2 + 2πrh = surface area of steel cylinder
Question:
Find the required radius of A = 125,000mm^2 and h= 150mm.
Thank you in advanced
Answer by Alan3354(69443)   (Show Source): You can put this solution on YOUR website!
A = pi*r^2 + 2pi*r*h = surface area of steel cylinder
---
Find the required radius of A = 125,000mm^2 and h= 150mm.
-------
That's the lateral area and one end.
A = pi*r^2 + 2pi*r*h = 125000
pi*r^2 + 2pi*r*150 = 125000
r^2 + 300r - 125000/pi = 0
-----------
Solved by pluggable solver: SOLVE quadratic equation (work shown, graph etc)
Quadratic equation (in our case ) has the following solutons:



For these solutions to exist, the discriminant should not be a negative number.

First, we need to compute the discriminant : .

Discriminant d=249154.943091895 is greater than zero. That means that there are two solutions: .




Quadratic expression can be factored:

Again, the answer is: 99.5771138806076, -399.577113880608. Here's your graph:

===============
r =~ 99.577 mm
Ignore the negative solution.

RELATED QUESTIONS

Hey i would like some help with this: The formula for the surface area of a cylinder is... (answered by Alan3354)
Hello, the following problem involves with finding the radius of a cylinder with just the (answered by Theo)
Find the surface area, to the neartest tenth, of a cylinder with diameter 5cm and height (answered by bob123132)
The surface area of a right circular cylinder of height 4 feet and radius r feet is given (answered by Fombitz)
2. In the surface area formula for cylinders, which of the following represents the... (answered by solver91311)
A=2πrh+2πr^2 (answered by robertb)
For the following exercise, determine the function described and then use it to answer... (answered by ankor@dixie-net.com)
Can someone help me with this problem please? The surface area of a sphere is directly (answered by kev82)
Could you assist me in solving a problem please? I can solve every problem in Chapter 2... (answered by josgarithmetic)