Add a Multiple of 10 to a 2-Digit Number
π 10, 20, 30... Blast off! Adding a group of 10 (like 20 or 40) is super fast because the "ones" place never changes.
Do this: Read the concept below, then try the quiz or activity.
Concept
A "multiple of 10" is any number that ends in a zero! (10, 20, 30, 40, 50).
π― 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: ___