Familiarisation task: Adding fractions with unlike denominators

Familiarisation task: Adding fractions with unlike denominators

Fractions Lab will not simply add fractions with unlike denominators for you. This sheet shows you how you can do it. Click here to download this worksheet.

The Task

Make 1/4 and 1/3 using the same type of representation. Extract the numerators by double clicking on them. Try to add them together by dragging them together and clicking 'add'. Watch the animation.

Why do you think Fractions Lab hasn't given you the answer this time?

What do you need to do to 1/4 and 1/3 so that Fractions Lab will add them together?

Use the 'find equivalent' tool to change 1/4 and 1/3 into fractions that Fractions Lab will add together. What fractions did you need to make? Add the two new fractions together.

Drag the three fractions into the 'add/subtract box'. What is the answer? 1/4 + 1/3 =

Teachers' Notes

This task takes students through several steps to add fractions with unlike 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. Therefore this task helps students to change the fractions into fractions with like denominators using the 'find equivalent' tool.

You could discuss with students how changing the fractions using the 'find equivalent' tool helps them to think about finding fractions with like denominators in a way that supports their conceptual understanding beyond using the algorithmic rule.

You can also read how to add fractions with unlike denominators by reading the Quick Start Guide, "Adding and subtracting fractions" and how to check them in "The operations box: compare, add or subtract".

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