Addition and subtraction within 20 - Subtraction crossing 10 - Presentation

In a series of engaging and educational slides, students are introduced to the concept of subtraction that involves crossing the ten boundary, an essential arithmetic skill. The lesson encourages the use of partitioning, a method where numbers are broken down into parts to simplify calculations. For example, students are asked to consider different ways to partition the number 5. They are then guided through practical examples, such as subtracting the number of jam tarts or bananas eaten from an initial amount, to demonstrate subtraction that crosses the ten boundary. The slides are designed to facilitate discussion and understanding of partitioning and its application in subtraction.

The presentation further delves into subtraction with the aid of ten frames and counters, providing visual aids that help students grasp the concept of crossing ten. For instance, the subtraction of 5 from 12 is made clear by using ten frames to show the partitioning of numbers. Students are prompted to use this method for other calculations, enhancing their fluency in subtraction. Reasoning activities challenge students to evaluate different methods of subtraction, such as partitioning 16 into 6 and 10, and to correct mistakes in calculations, like those made by a character named Zach. The slides encourage independent work, where students use number lines to complete calculations by partitioning, fostering a deeper comprehension of the strategy. Discussion points are provided to stimulate critical thinking about the various methods used to represent and solve subtraction problems.