Use Base-Ten diagrams and standard, expanded, and word forms to represent numbers. Warm up with a Mystery Math Mistake as you add two 2-digit numbers using a decomposition strategy. Find Which One ...

When you are solving an addition calculation with a two-digit number, you need to think about tens and ones. A place value chart can help you to see the value of each digit in a number. For example, ...

Column addition is a way of adding numbers together. It's helpful when you're adding two-digit or three-digit numbers together. When you do column addition, you lay out the numbers you are adding ...