Addition and Subtraction - Subtract two 4-digit numbers (one exchange) - Presentation

In a series of engaging activities, students are introduced to the concept of subtracting two 4-digit numbers with one exchange. The lesson begins with a discussion on how exchange relates to subtraction, setting the stage for deeper understanding. For instance, when faced with the problem of subtracting 2,126 from 5,533, students are challenged to consider if one can subtract 6 from 3 without making an exchange. The lesson guides them through the process of exchanging a 10 to facilitate the subtraction, which leaves the original number unchanged but alters the value of the digits involved for the calculation. This method is then applied to various examples, reinforcing the concept of exchanging when a digit in the minuend is smaller than the corresponding digit in the subtrahend.

Further activities require students to complete calculations that involve exchanging from different place values, such as tens or hundreds, depending on the subtraction problem at hand. For example, subtracting 1,572 from 3,655 necessitates an exchange of a 100 to successfully perform the operation. The lesson progresses with practice problems that solidify the students' understanding of column subtraction and the exchange process. Students are also presented with real-life scenarios, such as calculating the number of parents joining a school trip to the National Museum by subtracting the number of children and teachers from the total attendees. Additionally, reasoning activities challenge students to find missing numbers in subtraction equations and to explore patterns between the numbers. The lesson concludes with a discussion on strategies used when the digit being subtracted is smaller, and how concrete or pictorial representations can aid in understanding the exchange process.