lesson
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Imagine you have a magical mystery box. You know something is hiding inside, but you need math clues to figure out what it is!
A number sentence is a math line that uses numbers and symbols like +, −, and =. When a number is missing, we draw an unknown box (□) to hold its place.
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What happens when your friend hands you a mystery bag of stickers? Let's turn that story into math!
Adding Stories: Finding the Missing Part
Maya starts with 5 shiny star stickers. Her friend gives her a bag of more stickers, and now Maya has 12 stickers in all.
We start with 5, add the mystery amount □, and end up with 12. Our number sentence is 5+□=12.
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What if you start with a secret stash of cookies and eat some? Where does the mystery box go then?
Subtraction Stories: Mystery at the Start
Leo had a bowl of crunchy apples. He gave 4 apples to his brother, and now Leo has 6 apples left.
Leo started with an unknown number □, took away 4, and had 6 left over. We write this as □−4=6.
📊Interactive diagram