How can you apply formulas for perimeter, circumference, and area to find and compare measures?

Lesson 11-1 Areas of Rectangles (page 423) Essential Question How do you calculate the area of a rectangle?

Areas of Rectangles Rectangle Rectangular Region Area is measured in square units. u 2 vs. u vs.

The area of a square is the square of the length of a side. Postulate 17 s A = s 2 s s s

Also, the perimeter of a square is 4 times the length of a side. s P = 4s s s s

If two figures are congruent, then they have the same area. Postulate 18

The area of a region is the sum of the areas of its non-overlapping parts. Postulate 19

Any side of a rectangle (parallelogram) can be considered to be a base (b). b

Any segment perpendicular to the line containing the base from any point on the opposite side is an altitude. b

The length of an altitude is called the height (h). b h

The area of a rectangle equals the product of its base and height. Theorem 11-1 b A = b  h h

OR, the area of a rectangle equals the product of its length & width. ℓ A = ℓ  w w

The perimeter of a rectangle equals the twice length + twice width. ℓ w w ℓ P = 2ℓ + 2w … P = 2b + 2h

Example #1 The area of a square is 9 sq. cm. Find its perimeter. s s s s

Example #2 The perimeter of a rectangle is 20 cm. If its height is 4 cm, find its area. 4 cm b

Example #3 Consecutive sides of the figure are perpendicular. Find its area

u 2

Example #3 Consecutive sides of the figure are perpendicular. Find its area u u 2

Example #3 Consecutive sides of the figure are perpendicular. Find its area u 2 99 u 2 35 u 2

Example #3 Consecutive sides of the figure are perpendicular. Find its area u 2 99 u 2 35 u 2 A = 16u u u 2 = 150u 2

Assignment Written Exercises on pages 426 & 427 DO NOW: 1 to 19 odd numbers and GRADED: 25 to 29 odd numbers How do you calculate the area of a rectangle?