Regrouping is the process of combining ten individual ones into one ten. When adding, if you have 10 or more ones, you bundle them into a new ten and record the leftover ones. For example, 17 ones becomes 1 ten and 7 ones.
Use bundles of ten sticks or base-ten blocks to physically show this trading. Have students practice bundling 10 ones repeatedly until the concept is automatic.
You already understand place value: the tens place and the ones place. A number like 34 means 3 tens and 4 ones — not "thirty-four random dots," but a specific, organized structure. You also know addition facts up to 20. Regrouping is what happens when those two ideas collide: you're adding ones, and you end up with more than 9 of them.
Think about base-ten blocks. You have a pile of individual unit cubes (ones) and a pile of rods (each rod = 10 cubes bundled together). When you add 8 ones to 5 ones, you get 13 ones. But 13 loose cubes is messy and hard to compare with other numbers. So you trade 10 of those cubes for a single rod: now you have 1 rod and 3 cubes — that's 1 ten and 3 ones, or 13. This physical swap is exactly what the written "carry" notation records.
Here's what it looks like in a problem: 28 + 35. You add the ones column: 8 + 5 = 13. You can't write "13" in the ones place — that would put a 1 in the wrong column. Instead, you write the 3 in the ones place (the leftover after trading) and carry the 1 to the tens column (the new ten you just created). Then you add the tens: 1 + 2 + 3 = 6 tens. The answer is 63.
The "1" you carry is not just a reminder symbol — it represents a real ten that you created by bundling up 10 ones. This is why the "forgetting to add the regrouped ten" mistake is so costly: you literally lose a ten from your answer. Every time you carry, picture yourself handing that bundled rod to the tens column. Regrouping is not a trick — it's the place value system doing exactly what it was designed to do: keep ones with ones and tens with tens so big numbers stay organized.