Page 878 - Algebra 1

Estimate the Perimeter and Area of Figures
Skills Bank Lesson 17
Perimeter is the distance around a figure. The perimeter of a polygon is the sum of its side lengths. The area of a figure is the amount of surface it covers.
Perimeter and Circumference Formulas
Area Formulas
Rectangle P = 2l + 2w or P = 2(l + w) Circle C = 2πr or C = πd
Rectangle A = lw Circle A = πr2
Estimating Perimeter
a. Estimate the perimeter of the figure.
b. Estimate the perimeter of the trapezoid.
SOLUTION
Find the length of the top, side, and bottom of the trapezoid.
top: 4 units left: 4 units bottom: 9 units
Estimate the length of the diagonal line. diagonal line: ≈ 5 units
P ≈ 4 + 4 + 9 + 5 ≈ 22
The perimeter is about 22 units.
Example
1
8 feet
SOLUTION
8 feet
Estimate the length of the top, sides, and bottom of the figure.
right and left: ≈ 8 feet bottom: 8 feet
top: ≈ 8 feet
P ≈ 4(8)
The perimeter is about 32 feet.
Estimating Area
Estimate the area of the circle.
SOLUTION
Example
2
Estimate the area by counting the squares.
12 full squares 4 almost full squares
8 quarter full squares: ≈ 2 8 corners: ≈ 1 The area of the circle is about 19 units2.
Skills Bank Practice
a. Estimate the perimeter of the figure. b. Estimate the area of the figure.
Skills Bank 863
SKILLS BANK