Arithmetic Grade Five

Lesson One hundred and Fifty-six: More Perimeter and Area

	Finding the area of this shape is a little trickier. There are two general approaches to finding the area. In each case you must figure out the area of two rectangular areas and then you either add or subtract these areas depending on which method you use.
	Method One: full_width * full_height - adjacent_short_height * adjacent_short_width In this case you multiply the full width by the full height and then subtract away the product of the short width and short height which share a commond vertex. Using the example we have: 10 * 14 - 4 * 10 = 140 - 40 = 100 square units
	Method Two: full_height * width_1 + width_2 * height_2 In this case you multiply the full height by the adjacent short width and then add the product of the second partial width by the second partial height. Using the example we have: 10 * 4 + 10 * 6 = 40 + 60 = 100 square units Obviously, either method we use will yield the same answer.
	Method two allows you to split the shape in two different ways. 4 * 4 + 6 * 14 = 100 square units

Remember area is always represented in square units.

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