we know that
the total surface of a cylinder is equal to
[tex]SA=2B+Ph[/tex]where
B us the area of the circular base
P is the circumference of the circular base
h is the height of the cylinder
we have
h=2r
so
[tex]B=\pi\cdot r^2[/tex][tex]P=2\pi\cdot r^{}[/tex]substitute
[tex]SA=2(\pi\cdot r^2)+(2\pi\cdot r)\cdot h[/tex]substitute the value of h
[tex]\begin{gathered} SA=2(\pi\cdot r^2)+(2\pi\cdot r)\cdot2r \\ SA=2\pi r^2+4\pi r^2 \\ SA=6\pi r^2 \end{gathered}[/tex]therefore