Think of a parallelogram as a rectangle bended on its side. In this case, the rectangle is being bended from the right to the left. However, in this transformation, the area of the shape remains the same.
As such, you can apply the equation for the area of a rectangle here, Area = length * width.
However, now we are using different measurements. We have the base and the height of the parallelogram given.
The base acts as the width of the original rectangle. For reference, the top and bottom lengths of the rectangle were not changed as we were bending it into a parallelogram.
We also have the height given. Now, the left and right side lengths of the bended shape were changed. However, I want for you to conceptualize this, feel free to take out a piece of paper if it helps.
Draw out a rectangle that's longer left-to-right. Draw a bold line getting the height of the rectangle from one of the horizontal sides. Now, draw another bold line upwards through the middle of the rectangle. How do the bold lines compare? Are they the same?
Now, back to the example of the warping rectangle. When we're moving it towards the left, the left-right side lengths of the shape change. However, we can still get the height by drawing through the middle of the shape, which remains constant.
As such, we can confidently apply the area of a parallelogram formula,
Area = base * height.
The base acts as the width and the height acts as the length.
Area = 18 3/4 ft * 22 1/2 ft
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Apply the foil approach (First terms, Outer terms, Inner Terms, Last Terms):
Let a, b, c, d all equal some number. In this case, we can represent 18 3/4 as 18 + 3/4, representing variables a and b. We can do the same with 22 1/2.
Answer = a + b * c + d
Answer = (a+b) * (c+d)
Answer = ac + ad + bc + bd
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Area = 18 * 22 + 18 * (1/2) + 22 * (3/4) + (3/4) * (1/2)
Area = 421 7/8 ft^2