Addition and subtraction - Add two-digit and one-digit numbers - Presentation

In the fourth lesson of a series on addition and subtraction, students revisit the concept of adding two numbers together, particularly focusing on cases where the sum crosses the tens boundary. The lesson encourages students to think about the largest value that can be held in a place value column before moving on to practical exercises. The first activity involves mental addition, where students are prompted to hold a two-digit number in their head and count on with a one-digit number, such as starting from 17 and counting on 5. This method is repeated with different number combinations, reinforcing the mental arithmetic skills required for addition.

The lesson progresses to more efficient addition strategies using number bonds to bridge the ten. For example, the number 5 can be partitioned into 3 and 2, which helps to simplify the process of adding it to 17 by reaching a round number (20) and then adding the remaining 2 to find the total (22). This method is also applied to other number combinations, such as adding 6 to 16 by partitioning 6 into 4 and 2. The lesson includes activities that involve drawing the numbers in base 10 and showing the addition pictorially, which helps students visualise the process of exchanging 10 ones for one ten. Students are engaged in reasoning exercises to explain their answers and explore different possible totals, further developing their understanding of addition and number relationships.