Page 41 - ArithBook5thEd ~ BCC

6
4 1
1
(a) (b) 1 5
3
5 1
7
5

Solution. Adding the lengths of the sides, we find that the perimeter of polygon (a) is

3+ 4 + 1+ 5 + 5 = 18 ft.

Similarly, the perimeter of the polygon (b) is

7+ 5 + 6 + 1 + 1 + 1 = 21 ft.

Finding the area of a polygon can be complicated, but it is quitesimple if the polygon can bedivided
up into rectangles. A rectangle is a four-sided polygon with two pairs of opposite parallel sides, and
“square” corners. The square corners – also known as right angles – imply that the paired opposite
sides have the same length. The length of the shorter pair of sides is often called the width and denoted
w,and the length of the longer pair is called the length and denoted l.
l

width = w w

length = l

The small squares in the corners are there to indicate that the polygon is a rectangle.

Example 35. Estimate the area of the rectangle below, if the square in the upper left corner is 1 unit
on a side.

l

1

1
width = w w

length = l

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