Using loops to investigate 2D regular shapes 1 wk

Creating a Simple Scratch Program to Investigate Angles of Regular 2D Shapes
Computer Science Integrating with Maths Planning

Learning Objective

Lesson Plan

CS Objective
Understanding what a loop is
Maths Objective
Discovering what angles are used in regular 2D shapes

Start by explaining that we have lots of loops (repeated activities) in our lives
Use this very simple loop.pdf file to explain what a loop is. The activity builds from one school week into their whole school life. With younger pupils stop at One Whole Week.
Get pupils to stand up and put a single logo command within a loop. (e.g. repeat 3 forward one step)
Extend the activity to take in a couple of commands in a loop
Build the program

Get pupils to load up Scratch and shrink the cat to very small

Display the program blocks using this pdf file

Clears the screen and places the cat top middle facing right

Challenge pupils to build this program themselves
While they do this go round and make sure they are building scripts on the Cat sprite 1 and not the stage
Check that they have changed the numbers to match yours

Use the program
When they have finished draw them all together and explain that we are going to use this looping program to investigate what angles produce what regular 2D shapes.
Start from 170° and work down to 150° clearing the screen every time.

Explain that they only need to record on the sheet when they get to a regular 2D shape.
Pupils then go and use the program to investigate regular 2D shapes.
Half way through the activity briefly stop the class and explain that some shapes won’t be exact multiples of 10. If a shape looks like it might be close reduce the number of repeats/sides and try smaller increments.
When I did this lots of pupils found the pentagon at 72°

What did they discover?

What would they improve?
Class feedback

Cross Curricular Links

Able & SEN Support



Maths Objective
Discovering what angles are used in regular 2D shapes

Make sure they go back and reduce increments to find shapes that are not multiples of 10 such as the pentagon

Age and ability
I have done this lesson with mixed ability Year 3 pupils but it could be adapted for any lower KS2 year group.
Previous Experience
Some very basic use of Scratch before this lesson is helpful so that you don’t have to explain moving the blocks

Shape Investigator Sheet
Before the lesson create the program yourself in Scratch
Loop pdf
Program Instructions pdf