A cylinder has a surface area of 339 cm2 . The radius is two times greater than the height. What is the radius

PLzz help

if we say that the height is x high and the radius is then 2x wide.
This means that the top area will be pi*r^2 r = 2x so the area is pi * (2x)^2
(2x)^2 = 4x^2 so the top area is 4* pi * x^2
there are two of these so that is 8 * pi * x^2
then we have to work out the area of the middle bit
which is r or x times the cicumfrance of the top bit
r = 2x so
2 * pi * 2 * x = 4* pi *x
we then have to times this by the height x to give us
4 * pi * x^2
add this to the original bit
(8*pi*x^2)+(4*pi*x^2) which is 12*pi*x^2 this is = to 339 so now we have to solve
12*pi*x^2 = 339
x^2 = 339/12*pi
x = (339/12*pi)^0.5 =2.998709
2x(the radius) = 2* (339/12*pi)^0.5 = 5.99741754
If you check this it is slightly off because we are not using the full length of pi

i don't know the formula sor surface area but here are the values and you just plug it in and set it equal to 339cm^2.

r=2x

h=x

height is h and radius is r.

2piR^2 + 2piRh = 339
But R = 2h or h = R/2

So 2piR^2 + piR^2 = 339
R = sqrt(339/3pi) = 6.000 cm answer