Addition and subtraction - Subtract with two-digit numbers crossing 10 - Presentation

In a comprehensive lesson focused on subtraction, students delve into the concept of subtracting two-digit numbers, particularly when the calculation requires crossing the tens boundary. This lesson, part of a series on addition and subtraction, challenges students to consider what to do when there isn't enough in one column to subtract from another. The teaching slides encourage the use of a number line to assist with the subtraction process, prompting students to explore different methods such as subtracting ones before tens, or partitioning ones to reach the nearest ten before proceeding with the tens subtraction. This approach helps students understand the practical application of exchanging and partitioning in subtraction.

Throughout the lesson, various activities guide students through the subtraction process, using examples such as subtracting 12 from 51 or 25 from 48, and demonstrating how to reach the correct answer by breaking down the numbers. The lesson also includes reasoning tasks where students must deduce the most efficient method for subtraction, whether it's direct subtraction or counting back to find the difference. Additionally, independent work sections encourage students to apply the strategies they've learned to solve problems and word puzzles, reinforcing their understanding of the subtraction process and its intricacies when dealing with two-digit numbers and the crossing of tens.