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See the area and perimeter of any rectangle.
A random angle is shown on a "broken" protractor with a red arrow. Take a guess, then click "More info" to slowly put the protractor back together and finally see the measure.
Use this for a conversation for the perimeter and/or area of a complex polygon composed of non-overlapping rectangles. Drag the blue points to create a shape, then click one of the two buttons. Drag the sliders to move the sides.
An "Open Middle" format problem: What combination of digits and units would give you the greatest distance? What would give you the least? You must combine your number sense with an understanding of relative unit sizes as you develop a strategy.
A randomly generated (L-shaped) complex polygon starts as just two sides. Drag the sliders to make the rest. Meant to allow students to see the part/part/whole relationship between opposing sides.
Drag the point to change the dimensions of the rectangle. Then click the "Go" button to see the perimeter upwrap and the area fly out. Perimeter and area lie along the number line to allow conversations about their value. Works better for small rectangles.
Put various lengths (randomly generated) in the correct order. Select the units you want to use. Feedback provided.
Select the units you want to use, then guess the volume of the liquid in the container. Feedback provided.
This is a set of three dynamic illustrations meant to develop understanding of perimeter and area. "What's happening to the perimeter? What's happening to the area?" See also this student handout.
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