Surface area cylinder
The surface area of any shape can be found by adding together the surface areas of its parts.
If you always imagine pulling apart the cylinder and drawing it out you can clearly see that the areas are one rectangle and two areas of a circle (the top and bottom).
The area of the rectangle is Height = `h` multiplied by Length = `2\pir`
Area of rectangle = `h\times\2\pir`
The circle areas are:
Area = `\pir^2`
And because there are two circles
Area = `2\pir^2`
Area of a cylinder:
`h2\pir + 2\pir^2`
Ted has a cylinder of height 15 cm and diameter 8 cm. He calculates the curved surface area as
`2×\pi\times8×15`. Explain what he has done wrong.
He used the diameter not the radius (Circumference = `2\pir`)
He incorrectly multiplied by 2 when calculating the circumference (Circumference = `\pid`).