Place the shape on a grid and have child count the shaded squares. Let them know that is the area for the figure (the colored surface that covers the inside of the shape).
Then, have them count the number of squares across (5) and the number of squares down (4). Multiply the numbers and it will also equal the area A = 5 x 4 = 20.
Review the formula for area and explain:
Area = Length x Width (A= l x w) A = 5 x 4
A= 20 square units
Perimeter = 2 x width + 2 x length (P = 2W x 2L)
P = (addition of # of sides)
P = (2 x 5) + (2 x 4)
P = 18
Perimeter- The distance around a figure
Area- The number of square units used to cover the surface of the figure
Square unit- a square with a side length of one unit; used to measure area (i.e. cm2).
Divide figure to find area:
Divide the polygon into two rectangles. The larger rectangle measures as (4) length and (7) at the width. Use the formula for finding the rectangle (A = l x w) A = 4 x 7 = 28. Next, find the area of the smaller square which is (3) length and (3) width. A= 3 x 3 = 9. Finally, add the two areas together 28 + 9 = 37 sq. units.
Geo-board/ Dot Paper
Have the child practice drawing shapes and counting the number of squares it covers on the inside. Inform them that the number of squares it covers is the area in square units. The number of squares on that outlines the shape is the perimeter.