Addition and subtraction within 20 - Subtraction crossing 10 counting back - Presentation

In Lesson 10, students delve into the concept of subtraction, specifically focusing on the technique of counting back across the number 10. This method is essential for understanding how to subtract numbers that result in crossing the ten's boundary. For instance, starting from the number 14 and counting backwards is an example of this subtraction strategy. During the lesson, students are encouraged to discuss and practice counting back from various numbers, reinforcing their fluency and reasoning skills in subtraction.

The lesson features a practical scenario where students apply their counting back skills: Esin has 13 sweets in a jar and eats 5 of them. To find out how many sweets are left, students count back 5 from 13, crossing over the number 10 in the process, and arrive at the answer of 8 sweets remaining. The use of a number line is introduced as a visual aid to help students understand the concept of subtraction by counting back. Subsequent activities involve similar calculations, such as 14 minus 7 and 12 minus 3, with the number line serving as a tool to visually track the subtraction process. Finally, independent work consolidates their learning as they use the number line to solve additional subtraction problems and write down their answers.