7th Grade Section
WME@Kimpton Middle

Area of a Rectangle

Unit SquaresYou aleady know how to measure lengths. Basicaly you use standard lengths marked on a ruler to do it.

Now let's turn our attention to measuring surface area. We need area measurements for such common questions: how much wall paper do we need for your room? how many tiles are enough for the kitchen?

Square Unit for areaWe use a unit square as the basic unit for measuring areas. A 1cm square has an area of one square centimeter (cm2). An inch square has an area of one square inch (in2), and so on. We will find formulas for areas of common geometric shapes. But first we understand how areas are measured and why the formulas we will learn are indeed correct.

  1. Now let's get some practice measuring areas of a rectangle.

    Each square in the rectangle below is 1 cm by 1 cm. So each little square has an area of 1 cm2.

     

    Click on the little squares and see what happens to the area in red and area in green.

    What is the area of of the rectangle?  cm2

  2. The base of the rectangle is  cm. 

    The height of the rectangle is  cm. 

    The height × base is:  cm2.

    Area of a rectangleWith this demonstration, convince yourself that to obtain the area of a rectangle, we multiply its height by its base.

  3. Now create your own rectangle to measure:

    height =    cm and base =   cm  

     


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