Big Ideas Math Geometry, 2014
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Big Ideas Math Geometry, 2014 View details
Cumulative Assessment

Exercise 4 Page 60

Divide the figure into two triangles and a rectangle.

Perimeter: ≈ 24.6 units
Area: 36units^2

Practice makes perfect

Let's think about the perimeter and area one at a time.

Perimeter

To find the perimeter, we need the lengths of all sides of the figure. Two of these are parallel to the x-axis, so we can find their lengths by counting the number of squares between their endpoints.

The top and bottom sides are both 6 units long. We can find QT and RS using the Distance Formula. The coordinates of the points are Q(-4,3), T(-2,-3), R(2,3), and S(4,-3). First we will calculate QT.
QT = sqrt((x_2-x_1)^2 + (y_2-y_1)^2)
QT = sqrt(( -4-( -2))^2 + ( 3-( -3))^2)
Evaluate
QT=sqrt((-2)^2+6^2)
QT=sqrt(4+36)
QT=sqrt(40)
QT=6.32455...
QT≈6.3
The distance between Q and T is about 6.3 units. Now, let's calculate RS.
RS = sqrt((x_2-x_1)^2 + (y_2-y_1)^2)
RS = sqrt(( 2- 4)^2 + ( 3-( -3))^2)
Evaluate
RS=sqrt((-2)^2+(3-(-3))^2)
RS=sqrt((-2)^2+6^2)
RS=sqrt(4+36)
RS=sqrt(40)
RS=6.32455...
RS≈6.3
RS is also about 6.3 units. Finally, we can find the perimeter of the figure by adding together all of the side lengths. 6+6+6.3+6.3=24.6 units

Area

To find the area, we can divide the figure into a rectangle and two right triangles.

The base and height of both triangles are 2 and 6 units, respectively. To find their total area, we can use the formula for area of a triangle twice. 2A=2(b h/2) ⇒ 2(2( 6)/2)=12 units^2 The can calculate the area of the rectangle using the fact that the length is 6 units and the width is 4 units. A= l w ⇒ 6( 4) = 24units^2 The total area of the figure is the sum of the areas of the triangles and the rectangle. 12+24 = 36 units^2