Chapter 11 2 Geometry Name: _____________________________________________ Period: _______ Geometry Pad Activity: Discovering the Area of a Trapezoid Formula Objective: Write a formula for the area of a trapezoid in terms the bases and height. Step 1: Step 2: Step 3: Step 4: Open a new sketch in Geometry Pad. Select the shape tool and select Quadrilateral . -­‐ Tap the following 4 points in this order to create trapezoid ABCD. A(5, 6) B(9, 6) C(11,2) D(3, 2) Select the tool (bottom right). -­‐ Click on line segment AB. Turn on “Show Length”. Base1 AB = _____________ -­‐ Click on line segment DC. Turn on “Show Length”. Base2 DC = _____________
Create the height. Select the line segment tool and select segment. -­‐ Click on point A and the point (5,2) straight down to create segment AE. -­‐ Click on the segment AE. Turn on “Show Length”. Height AE= ____________ Stop and Think!! à 1.) Can you identify any other shapes within the trapezoid? 2.) Can you find the areas of each separate shape using the formulas you already know? 3.) Calculate the area of the trapezoid is using the areas of the shapes that you see. Step 5: Select the protractor tool and select measurements. -­‐ Click on trapezoid ABCD to show the area. Area  ABCD = ___________________ Did you correctly calculate the area of the trapezoid?!!? Chapter 11 2 Geometry Name: _____________________________________________ Period: _______ Observations: 1.)
Try drawing 2 trapezoids interlocked with each other to create a parallelogram. Can you think of another way to calculate the area of the trapezoid using this new shape? 2.)
Write your own formula for the area of a trapezoid using the bases and the height in the equation. Area of a Trapezoid Find the areas of the trapezoids. 1.)
2.)
3.) The Area of a trapezoid is 22.5 cm2. The bases of the trapezoid are 6 cm and 9 cm. What is the height of the trapezoid? Chapter 11 2 Geometry Name: _____________________________________________ Period: _______ Real-­‐life Example: Truss Bridge A truss bridge is a bridge whose load-­‐bearing structure is composed of a truss and connected elements forming triangular units and trapezoids. Truss bridges are one of the oldest types of modern bridges. A truss bridge is economical to construct because it uses materials efficiently. 1.)
If the Whipple Truss Bridge is 300 feet long, 40 feet high, and the top length is 270 feet, what is the area of the bridge. 2.)
If the bridge holds 10 tons for every 600 feet2, how many tons can the entire bridge hold safely? Hint, set up a ratio!