Question

what is the total surface area of a cylinder whose length is twice the radius

Answer 1

lateral surface area of a cylinder: 2πrh, r is the radius, h is the height.
area of the top and bottom circle: πr²
when h=2r, the total surface area is:
2πr(2r)+πr²+πr²=6πr²
the answer is 6πr²