Question

You need to make a soda can with a volume of 29 cubic inches.

Find the surface area. calculate the following:
a) How much material is needed if the can's radius is 2 inch?

Answer with the help of Reiny,
but doing it with a different radius
to make sure I got it.

let the height be h
volume = ðr^2h
ð(2^2)h = 29
h = ð/29

the surface area are
top + bottom + rectangle forming the outside of the cylinder
= 2ðr^2 + 2ðrh
= 2P(2) + 2ð(2)(ð/29)
= 54.13274 in^2

Since
Top = 12.56637 in^2
Bottom = 12.56637 in^2
Total surface if can radius is 2inch is: A = 54.13274 in^2

Answer 1

sorry:
ð = pi

Answer 2

After
2πr^2 + 2πrh , if r = 2, you forgot to square the 2 in the first term, should have been

2π(4) + 2π(2)29/π)

Make the necessary changes in your calculations
(I got 26.49)

BTW, even with your error how does
2π(2) + 2π(2)(π/29) = 54.13
I had 13.93
the first term of 2πr^2 is the sum of the top and bottom, since each is a circle of πr^2 )