You would use square metres (m2) to find the area of a door.
If it's a standard book, the standard units would probably be cm2.
Millimetres
You would find the area by multiplying the width by the length, so the area would be 216 square feet.
all you do is find the area of the circle... if you mean find the squares area, find the area of the circle, and then the square's area and subtract the squares area to the circles area
Same as you would find the area of any triangle A = (1/2)[base][height]
Square metre
Square meters.
square meter
Square metres
meters2
A square nanometer.
To find the area of a book cover in metric units, the most appropriate unit to use would be centimeters. The formula for finding the area of a book cover would be: length x width.
Square centimetres (cm2).
Square meters, generally.
Square centimetre.
To find the area of the door, get its length and breadth measurements then multiply them.
You would find millimetres on a ruler using metric.