Use models to add a two-digit and a one-digit number - with regrouping
Sometimes we have too many ones! π¦ Letβs learn how to trade 10 ones for a ten rod. This is called regrouping, and itβs a key to unlocking bigger addition problems!
Do this: Read the concept below, then try the quiz or activity.
Concept
Regrouping in addition is what we do when we have 10 or more 'ones'. We can't write a two-digit number in the ones place, so we have to trade them up!
Visual: Let's solve 27 + 5 using place value blocks. 1. Show 27 with 2 ten rods and 7 one cubes. 2. Show 5 with 5 one cubes. 3. Combine the ones first. You have 7 + 5 = 12 ones. 4. Oh no, that's more than 9! Take 10 of those ones and regroup them. Trade them for 1 new ten rod. 5. You'll have 2 ones left over. 6. Now, count your tens. You started with 2 rods, and you added 1 more from your trade. You now have 3 ten rods. 7. What do you have in total? 3 ten rods and 2 one cubes. That's 32! So, 27 + 5 = 32.
Key Idea: Any time you get 10 or more in the ones column, bundle 10 of them together and move them over to the tens column as a single ten.
Try it
Practice: Use models to add a two-digit and a one-digit number - with regrouping.