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All Lesson Plans

Logic Gates and Decision Trees

Overview and Objective

In this lesson, students will use logic gates to create a decision tree. Creating a functional decision tree will require students to have a thorough understanding of the functionality of logic gates. The tutorial page and truth table task might be a good place to start for those that need an introduction to logic gates.


Introduce this task to students by asking to discuss with a partner what weather conditions would be best for flying a kite. Allow a brief time for discussion and then have some students share with the class. Project this canvas to the class and discuss how it can be used to decide whether to fly a kite, go for a walk, or neither. Note that the purple rectangle is covering up the logic gates used in constructing this decision tree. As students work on building their own, you may consider removing the rectangle so students can see the gates.

Main Activity

Students will now create their own decision tree. Consider spending some time brainstorming either in small groups or as class a range of topics students might explore. Some possibilities:

  • Items needed to bring to school on a given day
  • Clothing needed depending upon the weather
  • What sporting team to root for based on a variety of scenarios

Students will likely need support as they working towards connecting various gates to create the outputs they want. At some point, perhaps sharing the link to the decision tree from the warm-up might be helpful. Alternatively, consider pausing students from their work and discuss as a class the supporting logic of the decision tree in the warm-up.

Remind students to frequently save their canvas. When they are finished, you can share some with the class. Click here to learn about creating classes in Mathigon and having students save their work.

Support and Extension

For students that may be struggling to make their tree work as intended, perhaps invite them to start with a simpler decision tree. Focusing on one input initially might help them understand the functionality of the gates and how to combine them together to add complexity. Additionally, if students have not completed the truth-table task, spending time on this might be helpful as well.

For students looking for additional challenge, encourage them to add additional complexity to their decision tree. Perhaps they could add another input to their current tree or create a new one with additional inputs. Additionally, as multiple students finish, invite them to share their decision trees with each other with a custom polygon covering the gates. See if students can determine the gates used on each other’s trees.

Polypad for this Lesson

Decision Tree - Original

Decision Tree – Polypad – Polypad

Decision Tree - Gates Covered

Decision Tree Covered – Polypad – Polypad