Addition and subtraction - Add and subtract 10s - Presentation

In the ninth lesson of a series on addition and subtraction, students are encouraged to extend their understanding of adding and subtracting by 10s. This lesson focuses on working with multiples of 10, where students are prompted to observe the patterns that emerge when these multiples are added to or subtracted from numbers. Through a series of slides, the concept is explored by discussing what happens to a number when 10s are added or subtracted, and students are asked to articulate their observations about the changes that occur in the number's digits.

Students engage in activities that involve continuing a number track by adding 20 each time, which helps to reinforce the concept of working with multiples of 10. They are also tasked with identifying the correct number sentence to find missing numbers in a sequence. Place value charts and concrete materials are used to further illustrate the concept, as students complete calculations and explore which columns in the place value chart change and which stay the same when 10s are added or subtracted. The lesson also includes reasoning exercises where students apply their understanding to practical scenarios, such as calculating the total number of crayons accumulated over a week and determining the value of rows and columns when different shapes represent different multiples of 10.