Lesson 1: Algorithms Unplugged: Tangrams

Unplugged | Algorithms


This lesson shows us something important about algorithms. As long as you keep an algorithm simple, there are lots of ways to use it. However, if you want to make sure everyone produces the same outcome, then your algorithm needs more detail. Students will learn the difference between a detailed and general algorithm while playing with tangrams.


By introducing a basic concept like algorithms to the class in an unplugged activity, students who are intimidated by computers can still build a foundation of understanding on these topics. Algorithms are essential to computer science. In this lesson, students will learn how to translate instructions into a algorithm and how that plays a role in programming.


Warm Up (10 min)

Main Activity (20 min)

Wrap Up (15 min)

Assessment (10 min)


Students will be able to:

  • Tackle the challenge of translating an image into actionable instructions.
  • Convey instructions to teammates in order to reproduce an image.
  • Analyze the work of teammates to determine whether an outcome was successful.



For the Teacher


  • Algorithm - A list of steps to finish a task.


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Teaching Guide

Warm Up (10 min)


  • Algorithm - Say it with me: Al - gor - ith - him

A list of steps to finish a task.

Lesson Tip

If your class has never used tangram pieces, you can choose to do an example for them or even have an entire tangram lesson. There are several good ones on the Internet. Here is a lesson that you can do in the classroom and here is a game that you can play online.


Your students may or may not have played with tangrams before. If they have, you can skip this portion, and move right to explaining the main activity.

Explain to the students that tangrams are usually used to solve puzzles. You receive a set of seven "tans" and must use them all (without overlapping any) to recreate an image that has been given to you. Often, this is done as an individual activity, and the player is allowed to see the image that they are trying to recreate. Many times, you can lay your pieces right on top of the image silhouette to be sure that the solution is just right.

Main Activity (20 min)


We are going to use our tangrams in a slightly different way than most. Instead of looking at our puzzles and trying to guess which shape goes where, we are going to get puzzles that already tell you where each shape goes.

You might think that this will make it easier, but it won't, because students will also not get to actually look at the image that we are trying to recreate! Instead, a teammate will be describing the image to us.

To keep it from getting too difficult, we will not use puzzles that require all seven pieces.


  1. Divide into groups of 3-5.
  2. Each player should cut out their own set of tangrams.
  3. Have one member of each group select an Algorithm Card without showing it to anyone else.
  4. The person with the Algorithm Card will try to explain the image to everyone else without letting them actually see it.
  5. The other players will build their pictures off of the description given by the Card Holder.
  6. When the Card Holder is done, everyone will show their pictures and see if they all ended up with the same image.
  7. If everyone ends up with the same drawing, the Card Holder can show the card and see if everyone matched the card.
  8. If any of the pictures in the group are different from each other, have the Card Holder try describing the image again, using more detail.
  9. Choose a new Card Holder and a new Algorithm Card and repeat until everyone has had a chance to describe an image.

Play through this several times, with images of increasing difficulty.

Wrap Up (15 min)

Flash Chat: What did we learn?

  • What did we learn today?
  • Was it easier or harder than you thought it would be to describe an image to one another?
  • Did any group end up having arrangements that all matched?
  • Can you share some tricks that you came up with that helped your group match the Image Card exactly?


Having students write about what they learned, why it’s useful, and how they feel about it can help solidify any knowledge they obtained today and build a review sheet for them to look to in the future.

Journal Prompts:

  • What did you learn today?
  • How do you feel about today's lesson?
  • Can you think of tricks to make it easier to describe tangram pictures to a partner?
  • Describe why you might want to be very detailed when creating algorithms for writing code.

Assessment (10 min)

Algorithms Unplugged: Tangram - Assessment

Pass out the assessment and allow time for students to complete it. If there is extra time, go over the answers as a class.

Standards Alignment

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CSTA K-12 Computer Science Standards

AP - Algorithms & Programming
  • 1B-AP-11 - Decompose (break down) problems into smaller, manageable subproblems to facilitate the program development process.