SOLUTION: A manufacturing firm wants to package its product in a cylindrical container 1 ft. high with surface area 4pi ftsquared. What should the radius of the circular top and bottom​ be

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Question 1142068: A manufacturing firm wants to package its product in a cylindrical container 1 ft. high with surface area 4pi ftsquared. What should the radius of the circular top and bottom​ be?
Found 2 solutions by josgarithmetic, ikleyn:
Answer by josgarithmetic(39617) About Me  (Show Source):
You can put this solution on YOUR website!
Cylinder Surface Area with Top AND Bottom,
2pi%2Ar%2Ah%2B2%2Api%2Ar%5E2
h being the length of height
r the radius


You have 2pi%2Ar%2A1%2B2%2Api%2Ar%5E2=4pi and you are asked for r.

Answer by ikleyn(52781) About Me  (Show Source):
You can put this solution on YOUR website!
.
The surface area of the cylinder is 


    SA = 2%2Api%2Ar%2Ah + 2%2Api%2Ar%5E2.


So, our equation is


    2%2Api%2Ar%2A1 + 2%2Api%2Ar%5E2 = 4%2Api  square feet,   or


    r + r^2 = 2,

    r^2 + r - 2 = 0

    (r-1)*(r+2) = 0.


Only positive root  r= 1 makes sense.


ANSWER.  The radius of the cylindrical container is 1 ft.

Solved.

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Ignore the solution by  @josgarithmetic,  since it is   W R O N G.


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After my note, @josgarithmetic re-wrote his post . . .