Triangle Explorer Lesson
Triangle Explorer Lesson Plan
Students learn how to calculate the area of triangles using
a variety of materials including computer applets.
Standards (NCTM 3-5)
Understand measurable attributes of objects and the units, systems, and processes
Apply appropriate techniques, tools, and formulas to determine measurements
- Understand such attributes as length, area, weight, volume, and size of angle
and select the appropriate type of unit for measuring each attribute
- Understand the need for measuring with standard units and become familiar
with standard units in the customary and metric systems.
- Develop strategies for estimating the perimeters, areas, and volumes of
- select and apply appropriate standard units and tools to measure length, area,
volume, weight, time, temperature, and the size of angles.
Students will need:
Students must be able to:
- perform basic mouse manipulations such as point,
click and drag.
- use a browser such as Netscape for experimenting with
- access to a browser.
- students will need pencil, paper, and rulers.
- Focus and Review
Students will calculate the area of different triangles using a variety of methods.
- Review any pertinent vocabulary.
- Tell the students that today they will be learning about area.
- Have all the students cut out a square. Do not specify the size.
(You may want to remind the students that the corners of a square are right angles.)
- Once the students have completed their squares, have them measure the area of their square.
- Have the students crease their square from the lower left corner to the upper right corner
and cut along the crease to create two right triangles with equal areas.
- Ask the students if anyone can tell the class the area of one or both of the triangles.
- Have that student explain to the class how he/she knew the area of the triangle.
- Teacher Input
- Remind the students that what they have been measuring is called area.
- Remind the students that area is measured in square units. These units can be
square m, cm, in, ft, etc.
- Ask the class to come up with a formula to calculate the area of right triangles.
- Tell them that they need to be able to explain why their equation should work for all right
- If no one mentions the length * width / 2 method, mention the method to the class
and have them try it.
- Show the students how to operate the Triangle Explorer Applet.
- Independent Practice
- Have the students work in pairs to explore the Triangle Explorer Applet.
- Instruct the students to work 5 easy problems, 5 medium problems, and 5 hard problems.
- If you need to have something to check, have the students draw
the computer generated shapes on a sheet of graph paper and write the
areas beside the shapes.
- Clarify how to calculate the area of a right triangle and ask if there are any questions.
- Discuss the different ways the students used to calculate the areas of more difficult