Question

"Medal if answered"

The surface area of a cylindrical can of radius r and height h is 2πr2 + 2πrh. If the can is three times as high as the radius of its top, express its surface area S as a function of r.

Answer 1

\[SA = 2\pi r^2+2\pi rh\]

And you are given that \(h=3r\)

so sub this into \(SA\); replace \(h\) with \(3r\),
and simplify

Answer 2

Im not sure those are the correct answers

Answer 3

\[SA=2\pi r^2+2\pi rh\]
\[h=3r\]
\[Therefore, SA = 2 \pi r^2 +2 \pi r(3r)=2 \pi r^2 + 6\pi r^2 = 8 \pi r^2\]
\[Hence, r = \sqrt{\frac{ SA }{ 8 \pi }}\]

Answer 4

thank you very much best mathmatician your a life saver !