Addition and subtraction - Add two-digit numbers crossing 10 - Presentation

The lesson on adding two-digit numbers when crossing the tens boundary is an essential step in understanding place value and the concept of 'exchange' in arithmetic. Students are encouraged to consider what happens when the sum in a place value column exceeds ten. For example, when adding 64 and 12, students break down the numbers into tens and ones: 4 ones plus 2 ones equals 6 ones, and 6 tens plus 1 ten equals 7 tens, resulting in a total of 76. This exercise helps to visualise the addition process and reinforces the understanding of place value. The lesson further explores the exchange process, where 10 ones can be exchanged for 1 ten, aiding in the simplification of addition calculations.

Further activities include practical examples such as finding the sum of two numbers like 67 and 25 or 37 and 28, and applying the concept of exchanging ones for tens to reach the correct total. Students are also given real-world problems to solve, such as determining the total number of pencils when combining the amounts from two classes, or the total bottles of glue from Eagle and Kestrel Classes. These activities not only solidify the mathematical concept but also make learning relatable to everyday situations. The lesson includes reasoning exercises where students are challenged to create their own calculations that require an exchange and to explain their methods using concrete or pictorial resources, promoting a deeper understanding of the addition process.