Addition and subtraction - Related facts - Presentation

The concept of related facts in addition and subtraction is an integral part of understanding mathematical relationships. In a series of engaging activities, students explore these relationships by comparing and contrasting different scenarios. For example, they are presented with two sets of marbles, one with 4 red and 2 green marbles totalling 6, and another with 40 red and 20 green marbles. Students are prompted to fill in the gap, applying their knowledge of addition to find that the total is 60 marbles. Similarly, they examine a situation with pens, where 3 blue and 4 black pens make 7, and then scale up to 30 blue and 40 black pens to find the total of 70 pens. These exercises encourage students to use concrete apparatus to visualise and understand the concept of scaling in related facts.

Further activities delve into part-whole models, where students complete the models by identifying the missing parts that make up the whole. This visual representation helps to reinforce their understanding of the relationship between addition and subtraction. For instance, they are shown that 10 is composed of 6 and 4, and similarly, 100 is made up of 60 and 40. Another task involves finding missing numbers in related facts, such as determining that 50 + 40 equals 90, and that 60 equals 100 minus 40. These exercises not only strengthen arithmetic skills but also encourage logical reasoning. The lesson concludes with reasoning tasks that prompt students to observe patterns and use base 10 knowledge to discern the relationship between numbers, further solidifying their grasp of the underlying principles of related facts in mathematics.