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Area is a measure of how much space there is inside a shape. It is the number of square units required to cover a 2-D object.

Calculating the area of a shape or surface can be useful in everyday life. For example, you may need to know how much paint to buy to cover a wall or how much carpet to buy to cover a floor in your home.

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Estimating the Area of Rectangles

A rectangle is a four-sided shape that has two sets of two sides that are equal in length. The longer sides are called the length while the shorter sides are called the width. All four corners are right angles. Right angles are usually shown by having a square drawn in the corner where the right angle is.

The area of a rectangle can be estimated using a variety of methods. One method is to use grid paper. Count the number of squares inside the shape. Each square is one unit.

Area = 6 x 3 = 18 square units

Prove it! Use a geoboard and construct a rectangle that is three squares wide and six squares long. How many squares are there inside the rectangle?

You can use a geoboard from your classroom or use the virtual geoboard by clicking here.

 

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Formulas are equations used to make specific calculations. To calculate the area of a rectangle, you would use this formula:

A = l x w

Area is always an amount “squared,” which is shown by writing the number 2 after and a little above the units.

For example, let's say you have a rectangle with a length of 4 mm and a width of 2 mm and you want to know what the area is, you could calculate it this way:

A = l x w                            

A = 4 x 2

A = 8 mm²

Notice that the answer contains mm². This is because any time you calculate the area of something, the answer must contain the unit it was measured in so that anybody looking at your work knows just how big of an area you have calculated.

If you didn't put in the unit, the answer could just as easily have been 8 km² or 8 m².

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