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Math and Arithmetic

Why it is possible for rectangles to have the same perimeters but different areas?


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July 11, 2009 9:17PM

This is possible because you add perimiters but multiply areas. Consider a 2 x 4 rectangle and a 1 x 5 rectangle. The first has a perimeter of 12 (2+2+4+4), and an area of 8 (2 x 4). The second rectangle has a perimeter of 12 also (1+1+5+5), but an area of 5 (5 x 1). The closer a rectangle is to a perfect square, the larger the area will be, because a square maximizes area. A 3 x 3 square also has a perimeter of 12, but an area of 9. Heres another way to think about it: a rectangle that is one inch tall and 100 inches wide would have a perimeter of 202 inches, and an area of 100 square inches. If you added one inch to the side so that it was 101 inches wide, you would add 2 inches to the perimeter, but only one square inch to the area. However, if you made it one inch taller, you would still add 2 inches to the perimeter, but you would DOUBLE the area to 200 square inches.