What is the surface of a cylinder radius 8mm height of 20 mm

Hey there :) You'll have to use the formula of cylinder to get your answer :
Surface area of cylinder : 2(pi)(r^2) + 2(pi)(r)(h)
pi = 22.7 or 22/7
r (radius of cylinder) = 8 mm
h = height of cylinder = 20mm

●Hence, just substitute your answer in the given formula and also don't forget to check whether the answer required needs to be in mm or cm.

Hope it helps :)

Cylinder Surface Area = (2 • π • r²) + (2 • π • r • height)
Cylinder Surface Area = (2*PI*8²) + (2*PI*8*20)
Cylinder Surface Area = 1,407.43