Addition and subtraction - Subtract one- from two-digit numbers - Presentation

In this mathematics lesson, students revisit the concept of subtracting a single-digit number from a two-digit number, with a particular focus on crossing the ten boundary. The lesson aims to deepen understanding of what happens to a number when we subtract from it. To achieve this, a series of activities are presented. The first activity encourages students to mentally subtract by counting back from a two-digit number, such as starting from 22 and counting back by 7. This is visualised through a sequence of numbers, with each subtraction of one represented, leading to the answer of 15. This method is repeated with different numbers to ensure students are comfortable with the process.

Further activities explore more efficient subtraction methods using number bonds to bridge the ten. For example, students learn to partition the number 7 into 5 and 2, subtracting in parts to find the result of 22 minus 7. This technique helps to simplify the subtraction process and aids in understanding the structure of numbers. The lesson also covers the column method for subtraction, where students learn to exchange one ten for ten ones to facilitate the subtraction of a larger number of ones. Through reasoning tasks, students compare different subtraction methods to determine which is the most efficient, and independent work tasks challenge them to apply these methods to various problems. The lesson is structured to encourage discussion and reflection on the methods used, ensuring that students not only perform the calculations but also comprehend the underlying mathematical concepts.