Make 4/5 and 2/5 using the same type of representation. Double click on each representation. This will extract the numerators. Drag the numerators on top of each other and once selecting 'subtract', watch the animation. Open the add/subtract box, select the subtraction symbol and then drag the three fractions into the box.
This task takes students through several steps to subtract fractions with like denominators. You may want to demonstrate these steps and ask students to follow them and to complete the accompanying worksheet that encourages them to reflect on their work.
It is worth noting that Fractions Lab will only add or subtract fractions that have like denominators. This is an intentional design decision to encourage students to consider the importance of identifying common denominators (i.e., identifying equivalent fractions where the denominators are the same) when they later move on to adding and subtracting fractions with unlike denominators.
You can also read how to subtract fractions with like denominators by reading the Quick Start Guide, "Adding and subtracting fractions" and how to check them in "The operations box: compare, add or subtract".Download Worksheet Next Task