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

In a comprehensive Year 3 lesson plan centred around addition and subtraction, students are introduced to the concept of adding three-digit numbers to two-digit multiples of 10, specifically focusing on scenarios where the sum crosses the 100 boundary. The lesson is designed to encourage mental calculation over column addition and begins with a starter activity that revisits counting in multiples of 10, highlighting that the units digit remains constant during this process. The class teaching input then engages students with bar models to identify missing parts and whole numbers, using stem sentences to reinforce the concept of parts making a whole. Practical activities are incorporated, using place value counters and mats to visually represent the addition process and to illustrate the concept of exchanging ten tens for one hundred.

During the independent learning phase, children work in pairs to explore different strategies for addition, such as using known number facts to adjust calculations for efficiency. They practice this with specific examples and are encouraged to use reasoning to solve missing number problems with the aid of bar models and number lines. The plenary involves reflection on the methods used and a discussion on common misconceptions, such as recalling the next multiple of 100 and accurately counting in tens. To ensure understanding at different levels, the lesson plan includes differentiated activities for working towards expected, at expected, and at greater depth levels. These include step-by-step guidance on exchanges using place value charts, exploring the concept of crossing ten through various tasks, and solving more complex problems involving missing numbers.