Quadratic growth
Growing shapes

The Shape editor tool helps you display a series of shapes built from small squares. You can also use it to investigate the counting function that describes the dependence of the number of squares making up a shape on its serial number.


Investigate functions describing series of shapes

Select one of the series of shapes from the Examples menu. The tool shows the first four shapes in the series (you may have to scroll laterally to see all four shapes). Click the new button to add a fifth shape. Draw the shape in the window on the right, then click the update button.

  • Present the value table and graph of the counting function for the series of shapes, as well as its change. Can you use this data to predict the number of squares in the sixth shape in the series?

  • Construct a correspondence rule for the counting function. You can enter the correspondence rules at the bottom of the tool, then present their graphs. Use the correspondence rule to predict the number of squares in the sixth shape in the series.

  • Add a sixth shape and check your previous predictions.

  • Describe interesting ideas that came up in your work with series of shapes. Give examples. Some questions to consider:
    - What series of shapes define counting functions with linear growth? When do you obtain quadratic growth? Are there series of shapes for which the function is neither linear nor quadratic?
    - Relations between different series of shapes: Are there cases in which you can use the correspondence rule you constructed for one series of shapes to construct a correspondence rule for a different series?
    - Is it possible to construct two different correspondence rules for the same series of shapes by using different approaches? How can you prove that two different correspondence rules define the same function?
    - Is it possible to find different series of shapes that have the same counting function?
    - What questions about large shapes can you answer based on one of the representations of the counting function?








  • Quadratic growth
    From value table to change

    Building blocks
    Growing shapes
    Saving the elephants
    Holiday cards
    Allowance
    Jackpot
    International calls
    Matchstick shapes
    Computer network
    Cutting the cake
    Correspondence rules and quadratic growth