Surface Area of Cylinders

Look at this cylinder.

 

 

It's net is made up of two circles and a rectangle.

 

 

 

 

 

Remember that:

the Area of a circle of radius r = πr²

the Circumference of a circle of diameter d = πd

 

 

Look at these diagrams to see that the base of the rectangle has the same length as the circumference of the circle. 

 

 

So the Surface Area = 2πr² + πdh = 2πr² + 2πrh

 

Example

Find the surface area of this cylinder in cm² to 3 significant figures.

 

Answer

Diameter = 6 cm

Radius = 6 ÷ 2 = 3 cm

Height = 12 cm

 

Surface Area = 2πr² + 2πrh  = 2 x π x 3² + 2 x π x 3 x 12 = 282.74 ≈ 283 cm² (3 s.f.)