Friday, May 27, 2011

Triangles and Quadrilaterals

ABC is a triangle with base b and height h. Points D and E are midpoints of AB and BC, respectively.

1. Move the slider h to determine the height of the triangle.
2. Move points A, B, and C to choose the shape of the triangle.
3. Move the circle in slider t to the extreme right transform the triangle into a quadrilateral.
4. Click check box to hide the triangle.

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1.) After moving slider t, what type of quadrilateral is formed?
1.) What is the relationship between the area of the triangle and the area of the quadrilateral?
2.) Find the area of the triangle in terms of b and h.
3.) Find the area of the quadrilateral in terms of b and h.

Download Applet


  1. This seems like a brilliant activity.
    But am I wrong or does it have several layers requiring much more detailed questioning?
    For eg. the student has to first recognise that D & E are the mid points.
    Then use similar triangles to find the relationships between the two heights.
    Use the midpoint theorem to prove that the quadrilateral obtained ia a parallelogram......
    Or am i making this too complicated?

  2. Sneha:

    Thank you. Before we give this activity to students, they should know the pre-requisite knowledge about the proof. D and E as midpoints are already given above. :-)

    by the way, please check my other blog: You might find it interesting.