Method #1 – Area from Length & Width
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Formula – How to calculate the area of a triangle using the Length & Width
Area = Length x Width
Example
A rectangle has a length of 10 and a width of 30
Area = 10 x 30 = 300
Method #2 – Area from Perimeter
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Formula – How to calculate the area of a triangle using the perimeter
Step 1 – Find the length of the other side
Width = (Perimeter – Length – Length) ÷ 2
Step 2 – Find the area of the rectangle
Area = Length x Width
Example
A rectangle has a length of 10 and a perimeter of 60
Width = (60 – 10 – 10) ÷ 2 = 40 ÷ 2 = 20
Area = 10 x 20 = 200
Method #3 – Area from Diagonal
Formula – How to calculate the area of a rectangle using the diagonal
Step 1 – Find the width of the other side
Width = √(Diagonal2 – Length2)
Step 2 – Find the area of the rectangle
Area = Length x Width
Example
A rectangle has a length of 10 and a diagonal of 30
Width = √(302 – 102) = √(900 – 100) = √800 = 28.2842
Area = 10 x 28.2842 = 282.842