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Mathematics
Problem
A hollow metal cylinder is open at both ends. To calculate the amount of metal sheet required to make it, which of the following expressions should be used? (Here
r
r
r
is the radius and
h
h
h
is the height.) a)
π
r
2
+
2
π
r
h
\pi r^{2}+2\pi r h
π
r
2
+
2
π
r
h
b)
2
π
r
(
h
+
r
)
2\pi r(h+r)
2
π
r
(
h
+
r
)
c)
2
π
r
h
2\pi r h
2
π
r
h
d)
π
r
h
\pi r h
π
r
h
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