Addition and subtraction - Subtract a two-digit number from a ​three-digit number crossing 100 - Presentation

In this comprehensive lesson, students are tasked with mastering the skill of subtracting a two-digit number from a three-digit number, focusing specifically on calculations that involve crossing the 100 threshold. The lesson commences with a discussion on various subtraction methods, such as the number line and column method. Following this, the class moves on to a series of engaging activities. The first activity encourages students to count back in tens using a number line to solve subtraction problems like 530 minus 60, reinforcing their understanding of the concept. This visual approach aids in grasping the subtraction process and the significance of crossing the 100 mark.

Further activities delve deeper into subtraction strategies. For example, students are presented with a part-whole model to explore the breakdown of numbers in subtraction, such as decomposing 634 into 600 and 34, then subtracting 70 in parts to find the answer. The lesson also challenges students with reasoning exercises, where they must find missing numbers in subtraction equations and justify their methods. These exercises not only test their arithmetic skills but also their logical reasoning and ability to articulate their thought processes. Independent work tasks include filling in missing digits and discussing various methods, allowing students to reflect on their preferred strategies and the reasoning behind them.