Create a new Scratch project and delete the cat sprite.

https://scratch.mit.edu

Show: Scratch: How to create a new project

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Go to the Scratch website using the link below and click on the 'Create' link in the blue bar at the top.

By default, each new project starts with the cat sprite already added. To delete the cat click on the x in the blue circle beside the cat in the sprite list.

https://scratch.mit.edu

Add the 'Stars' backdrop to your project from the backdrop library.

Show: Scratch: How to add a backdrop from the library

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To add a backdrop from the backdrop library follow these steps:

1. Put your mouse over the Choose a Backdrop button
2. Click on the magnifying glass
3. Find the backdrop you want in the library
4. Click on your chosen backdrop

You can use search box or the filter links (Fantasy, Music, Sports etc) to locate your backdrop.

In this lesson we will be calculating how long it takes to go all the way around the world depending on what speed you are travelling. The circumference of the earth is 40,075 kilometers around so the math formulas we will be using are:

• how long in hours = 40,075 / speed (kilometers per hour).
• how long in days = (40,075 / speed) / 24 (we divide by 24 as there are 24 hours in a day).

To help us with these formulas we will need two variables. Create two new variables by clicking the 'Make a Variable' button.

1. 'earth' this will store the circumference of the earth (40,075 km)
   
2. 'amount' this will store the answer when we perform a calculation

Show: Scratch: How to create a variable

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In the Variables palette, create a new variable by clicking the 'Make a Variable' button.

Once you click this button a box will appear asking what you want to call your variable. Give it a name that reminds you what you will be using it for. For example, if you wanted to keep track of your score in a game, you would create a variable called 'score'.

Add the 'Earth' sprite to your project from the sprite library and then give it the following code.

when green flag clicked hide variable [amount v] hide variable [earth v] set [earth v] to (40075) // the earth's circumference go to x (0) y (0) // place it in the center

Show: Scratch: How to add a sprite from the library

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To add a sprite from the sprite library follow these steps:

1. Put your mouse over the Choose a Sprite button
2. Click on the magnifying glass
3. Find the sprite you want in the library
4. Click on your chosen sprite

You can use search box or the filter links (Animals, People, Fantasy etc) to locate your sprite.

Next lets use some say Hello! for 2 secs blocks to give some information and instructions.

Add the following code new code to the Earth sprite underneath the go to x: 0 y: 0 block.

when green flag clicked hide variable [amount v] hide variable [earth v] set [earth v] to (40075) go to x (0) y (0) // add new code under here say (join [The circumference of the earth is ] (join (earth) [ kilometers])) for (5) seconds say [Choose how you want to go around the world by clicking on an option below.] for (5) seconds