Addition and subtraction - Add a two-digit and ​three-digit number crossing 10 or 100​ - Presentation

The lesson plan introduces students to the concept of adding a two-digit number to a three-digit number, particularly focusing on situations where the sum crosses the tens or hundreds boundary. The aim is to understand what occurs when the sum in a place value column exceeds 9. The first activity encourages students to use base 10 blocks to visually represent the addition of numbers like 38 and 452, prompting discussions about exchanging 10 ones for a ten and the implications on the other place value columns. This concrete representation aids in grasping the abstract concept of carrying over in addition.

Further activities build on this foundation, where students are tasked with representing and solving different addition problems using base 10 blocks. They are guided through the process of exchanging 10 tens for a hundred and employing column addition to complete the calculations. For example, adding 45 to 264 and 329 to 68, with the results clearly demonstrated using base 10 representations. The lesson also includes reasoning tasks, such as evaluating Malachi's incorrect addition of 265 and 67, to help students understand the importance of correct exchanging in addition. Additionally, students are encouraged to discuss different methods for solving addition problems, such as the column method, using base 10, or adjusting numbers before adding, fostering a deeper understanding of the concepts and flexibility in problem-solving.