Addition and Subtraction - Add 2 four digit numbers (more than one exchange) - Presentation

In Lesson 6 of a mathematics presentation, students tackle the challenge of adding two four-digit numbers that require more than one exchange. The lesson begins by prompting students to think about when an exchange is necessary during addition. They then move on to a hands-on activity where they use place value counters alongside written calculations to add two specific four-digit numbers, starting from the ones column. This exercise highlights the concept of 'chaining' exchanges, where multiple digits in a column result in a sum that exceeds nine, necessitating an exchange to the next highest place value. Students are encouraged to explore this further by creating additional questions that produce a similar chain of exchanges.

Following the initial activity, students delve into comparison exercises, adding comparison symbols to make number sentences correct. This reinforces their understanding of addition and the size of numbers. A character named Malachi introduces a reasoning challenge, suggesting that only one exchange is possible per column when adding any two numbers. The presentation confirms Malachi's claim, explaining that the maximum value in any place value column is 18, thus only one exchange is necessary. Another reasoning task has students consider multiple possible answers for missing numbers in a sum, with the correct reasoning involving an exchange from the tens to the hundreds column. The lesson concludes with independent work, where students use place value counters to solve calculations, comparing this method with the numeric representation and discussing the exchanges made during the process.