Addition and subtraction - Add two three-digit numbers ​crossing 10 or 100​ - Planning

In the Year 3 curriculum, students encounter a pivotal mathematical concept: adding two three-digit numbers that require crossing tens or hundreds. This process is also known as 'exchanging'. During the lesson, children begin by revisiting the basics of place value, which lays the foundation for their understanding of addition. They are introduced to practical resources, such as place value mats, coins, and worksheets, to help visualise the process. Key vocabulary terms like 'place value', 'digit', 'exchange', and 'addition' are emphasised to ensure that students are familiar with the language of the subject.

The lesson progresses by guiding students through exercises that start with single exchanges and advance to problems requiring multiple exchanges. Visual aids, such as Base 10 or place value counters, are employed to model the concept concretely, and students are encouraged to record their findings using the column addition method. This approach helps them grasp when and why an exchange occurs. To deepen their understanding, students engage in independent work with differentiated worksheets and reasoning tasks that prompt them to explain their thought process using structured sentences. The lesson aims to build fluency and confidence in adding three-digit numbers, while also addressing common misconceptions such as misaligning place value columns or exchanging when it's unnecessary. By the end of the lesson, students are expected to understand the process of exchanging and apply it to increasingly complex problems, with the ultimate goal of achieving greater depth in their mathematical reasoning.