Addition and subtraction within 20 - Add by counting on 2 - Presentation

The lesson on addition and subtraction within 20, specifically focusing on the concept of adding by counting on, is designed to enhance young students' fluency and reasoning skills. It introduces the idea that addition is commutative, a term that may be new to some students, prompting them to explore its meaning. The lesson employs various representations, such as ten frames and number lines, to illustrate the process of counting on from a given number. Students are encouraged to engage with number stories, for example, by determining the total number of cars in a car park after more cars arrive, or the total number of ladybirds in a group after more join. This approach helps students visualize and understand the addition process in a practical context.

Further activities involve real-life scenarios where students calculate the total of items or tokens after additional ones are added. For instance, they determine how many prize tokens Esin has after winning more, or how many Lego pieces Zach has after buying extra. These activities are designed to solidify the students' understanding of addition by counting on. The lesson also includes reasoning tasks where students can create their own number stories and use practical equipment, such as counters, to represent addition. They compare different methods of counting on and discuss which they prefer and why, discovering that addition is always commutative regardless of the starting point. Independent work challenges students to apply their knowledge to various problems, encouraging them to explain their thinking and verify the correctness of given calculations.