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Grade 1 Math · Level 2, Add & Subtract to 20

Use Related Facts Within 20

How the lesson starts: Use Related Facts Within 20

1. The fact treehouse

   Hi friend! Look at this treehouse. Three numbers live here. 8, 4, and 12. They are a fact family! If you know one fact, you know more. Let's visit!

2. An adding fact helps

   8 red apples and 4 green apples. 8 + 4 = 12. Now 8 red ones roll away. 4 are left. 12 − 8 = 4. Same three numbers!

3. Which fact helps?

   6 + 6 = 12. Which fact also helps? 12 − 6 = 6. Yes! The whole, 12, goes first. 6 − 6 = 12? No! Watch out! Take away always starts with the whole.