K-5 friendly lesson

Try one idea, then jump into the activity.These lessons are designed to feel short, friendly, and easy to follow.

Add a Multiple of 10 to a 2-Digit Number

🚀 10, 20, 30... Blast off! Adding a group of 10 (like 20 or 40) is super fast because the "ones" place never changes.

Lesson 1

Concept

A "multiple of 10" is any number that ends in a zero! (10, 20, 30, 40, 50). 🎯 **The "Tens Only" Trick:** **Example: 34 + 20 = ?** Look at the ones place. 34 has a 4. 20 has a 0. What is 4+0? It's 4! The ones place STAYS THE SAME! You only have to add the Tens place together. 1. **Cover up the ones place!** Just look at the tens. "3 + 2 = 5". 2. **Put the 5 in the tens place:** The answer will start with a 5. 3. **Bring back the ones place:** Bring back the 4! So, **34 + 20 = 54**! You just skipped all the hard math by focusing on the tens.

Try it

Add the tens! **Instructions:** Add the multiples of 10 by changing ONLY the tens digit! **Problem 1: 45 + 30 = ?** * Just add the tens! (4 + 3 = ___) * Keep the ones! * Answer: ___ **Problem 2: 61 + 20 = ?** * Answer: ___ **Problem 3: 28 + 40 = ?** * Answer: ___ **Problem 4: 17 + 50 = ?** * Answer: ___ **Problem 5: 39 + 10 = ?** * Answer: ___