A two-digit number is composed of groups of tens and leftover ones. For example, 24 is 2 groups of ten plus 4 ones. Understanding this regrouping is key to working efficiently with addition and subtraction. Using manipulatives like base-10 blocks helps students see this relationship concretely.
Use base-10 blocks, bundled sticks, or ten-frames to show how numbers are composed of tens and ones. Have students physically group objects and count them.
You already know how to skip count by 10s: 10, 20, 30, 40, and so on. Place value is the idea that those jumps of ten are built right into how we write numbers. When you see the number 24, the "2" doesn't mean 2 — it means 2 groups of ten, or 20. The "4" means 4 leftover ones. So 24 = 20 + 4, which is the same as 2 tens and 4 ones.
Think of it like bundling pencils. If you have 24 pencils, you could bundle them into 2 groups of 10 with 4 pencils left loose. The tens place (the left digit) tells you how many bundles you have. The ones place (the right digit) tells you how many are left over. Base-10 blocks work the same way: a long rod represents 10, and a small cube represents 1.
This is why the position of a digit matters so much. The "2" in 24 and the "2" in 42 are very different — one means 2 tens (20) and the other means 2 ones (2). The value of a digit depends entirely on where it sits. That's the core insight of place value: position determines value.
Once you can see any two-digit number as tens and ones, addition and subtraction become much easier. Instead of counting 36 + 21 one by one, you can add the tens together (30 + 20 = 50) and the ones together (6 + 1 = 7), giving you 57. Breaking numbers apart into tens and ones is the foundation of every arithmetic strategy you will learn from here on.