Class 2 · Topic 2
Addition & Subtraction to 20
Step 1 · Learn
Read the ideas
- ➕🔒
Adding Within 20
Start at the bigger number and count on.
- 👯🔒
Doubles & Near-Doubles
A near-double is one more than a double.
- 🔟🔒
Make Ten to Add
Make a ten, then add what is left over.
- ➖🔒
Subtracting Within 20
Start at the number and count back.
- 🌳🔒
Fact Families
Three numbers make two adds and two subtracts.
- 🧩🔒
Missing Numbers & Adding Three
Subtract to find a gap; add three two at a time.
Step 2 · Practice
Try the quests
Step 3 · Boss Battle
Beat the boss
🛡️ 🛡️ 🛡️ 3 shields — lose all → 60-second cooldown
Round 1
A robot starts on 9 and hops on 6 spaces.
🔒Round 2
The next robot knows 7 + 7 = 14. It now…
🔒Round 3
A dial reads 8 + 7. Then 2 more are added.
🔒Round 4
A tank shows 16. It loses 7, then loses 3…
🔒Round 5
One lock uses the family of 5, 9 and 14.
🔒Round 6
The final code sentence is 4 + ? + 6 = 17.
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