Addition and subtraction - Add two-digit numbers - Presentation

In a series of engaging mathematics lessons, Year 3 students revisit the concept of adding two-digit numbers, with a particular focus on crossing the tens boundary. This involves exploring when and how to exchange ten ones for one ten during the addition process. The lesson slides guide the students through various activities that encourage them to practise and understand this concept. For instance, they begin by calculating the sum of two two-digit numbers, such as 64 + 12, by first adding the ones (4 + 2) and then the tens (6 + 1), before combining the two to find the total sum. This activity reinforces their understanding of the value of digits within numbers and the importance of correct place value alignment when performing addition.

Subsequent activities delve deeper into the exchange process, where students learn to recognise when the sum of the ones exceeds ten, necessitating the conversion of ten ones into an additional ten. For example, when adding 35 and 26, students partition the numbers into tens and ones, add them separately, and then exchange ten ones for one ten to find the correct total. The lesson structure includes opportunities for reasoning, where students can create their own calculations that require exchanging, and for independent work, where they can practise the methods they have learned. Throughout the lesson, students are encouraged to discuss their strategies and understanding, ensuring they grasp the concept of exchanging in addition and can apply it confidently to various problems.