Addition and subtraction - Subtraction crossing 10 - Presentation

In Lesson 13, the focus is on mastering the concept of subtraction when the result requires 'crossing 10'. This means that during the subtraction process, students will move past a tens boundary. For example, subtracting a number from 67 requires counting back in ones, crossing from the sixties into the fifties. The lesson uses visual aids such as number lines and encourages discussion on strategies for effective subtraction. Students are prompted to think about how partitioning a number can aid in the subtraction process, breaking it down into smaller, more manageable parts.

Through a series of engaging activities, students are presented with practical examples, such as subtracting the number of eaten jam tarts or bananas from an initial amount, to illustrate the concept of crossing 10. The use of ten frames and counters offers a visual representation to help students understand and apply the subtraction strategy. They are encouraged to use these tools to calculate differences, such as 12 minus 5, and to explore partitioning techniques that simplify the process. Additionally, reasoning questions challenge students to analyze and correct mistakes, such as incorrect uses of the equals sign or the misapplication of subtraction strategies. The lesson aims to build fluency in subtraction across tens boundaries and to foster critical thinking through problem-solving and discussion.