Answer:
Write the formula for one measurement, then solve the formula for the different measurement you want to find and use this new formula to find that measurement.
Step-by-step explanation:
We can understand this through an example.
If we need to find the lenght of a rectangle whose width is 4 feet and whose perimeter is 28 feet, we can use a formula for one measurement to write a formula for a different measurement:
- We need to write the formula for the perimeter of a rectangle:
![P=2l+2w](https://tex.z-dn.net/?f=P%3D2l%2B2w)
Where "l" is the lenght and "w" is the width.
- Since we know the width and the perimeter of the rectangle and we need to find the lenght, we can solve for "l":
![P=2l+2w\\\\P-2w=2l\\\\l=\frac{P-2w}{2}](https://tex.z-dn.net/?f=P%3D2l%2B2w%5C%5C%5C%5CP-2w%3D2l%5C%5C%5C%5Cl%3D%5Cfrac%7BP-2w%7D%7B2%7D)
Now we get a new formula for calculate a differente measurement (the lenght of the rectangle).
- Substituting values, we get:
![l=\frac{28ft-2(4ft)}{2}=10\ ft](https://tex.z-dn.net/?f=l%3D%5Cfrac%7B28ft-2%284ft%29%7D%7B2%7D%3D10%5C%20ft)