Cat and Mouse on Scratch
Kyle Murphy teaches 6th through 8th grade math at St. Joan of Arc Catholic School in Indianapolis. After teaching for six years with some technology integration, he is now developing a mathematics classroom that is more fully integrated with 1:1 technology. Mr. Murphy completed a master's degree in K-8 Mathematics Education at Ball State University. You can contact Kyle at kmurphy at sjoa dot org

What follows is a lesson on translations using the Scratch program. Mr. Murphy updated his screen shots from the original lesson because Scratch is now Web based.

Abbreviated Lesson Plan
Motivator: Introduce the lesson with a video on translations and discuss. [The video is now offline.]

Cat Moving: Start with the Cat Moving code to demonstrate what happens in translations.
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The code above is what I used. Put some different positive and negative values in for the changes and ask students where the cat will end up. Play the actions to see what happens. Let students input some values to see other examples. Ask students what the cat did and what it did not do.

Multiple Translations: I used the Cat Translations code below to have students test out multiple movements. The students needed to come up with four changes in x and y that would move the cat four times and end up back at the origin.
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Have a few students input their moves and observe the results. Discuss how students came up with the changes they used. You can also do another round where the cat starts and ends at a point other than the origin.

Cat and Mouse: Use the Cat and Mouse code below to do an informal assessment of what students understand.
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Above is the code for the cat sprite, and below is the code for the mouse.
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Each mouse will need to be programed with a different starting location in the “go to” block.
Have students check their solutions to the Cat and Mouse code, there are multiple solutions, depending on which order the student sends the cat to catch the mice.

Sample Student Answers:

__High Performance__ - Student used the right numbers and right number of movements to solve the problem correctly.

__Middle Performance__ - Student came up with correct solution, but used too many movements.

__Low Performance__ - Student did not start with cat at origin. The student’s solution starts at each of the mice and then uses four moves to get to zero.

Assessment: To assess the students I used a worksheet. Here are some examples of the types of questions I asked.

1. A sprite starts at (0,0) and moves 10 units right and 50 units down. What are the coordinates of the sprite’s new location?

2. A sprite starts at (3, -15) and moves 20 units right and 42 units up. What are the coordinates of the sprite’s new location?

3. Below are commands for a Scratch sprite that starts at (0,0). Fill in the missing numbers so that the sprite will end up back at (0,0).

change x by
change y by

change x by

change y by

change x by
change y by

change x by

change y by