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Grade 2 Math · Level 4, Arithmetic within 100

Addition Within 100

Add one- and two-digit numbers accurately and fluently, including regrouping.

How the lesson starts: Addition Within 100

1. Moon rock hunt

   Blast off! Astronaut Kai is on the moon. She found 34 moon rocks. Then she found 25 more! How many rocks in all? Let's add!

2. Jump by tens

   Adding tens is easy. Start at 45. Add 30 by jumping ten at a time: 55, 65, 75! The ones digit stays the same. 45 + 30 = 75.

3. Tens and ones

   Let's solve 34 + 25. Break 25 into 20 and 5. Add the tens: 30 + 20 = 50. Add the ones: 4 + 5 = 9. Put them together: 50 + 9 = 59!