Dividing fractions
Divide a fraction by a fraction using the 'keep-change-flip' method and visual models; interpret and solve word problems involving division of fractions by fractions
What a learner can do afterwards
- Divide a fraction by a fraction using the reciprocal method
- Use visual fraction models to represent and explain fraction division
- Create story contexts for fraction division problems and solve them
The lesson
You already know two skills: multiplying fractions, and dividing a fraction by a unit fraction like 1/4. Dividing a fraction by any fraction uses those same skills plus one new trick, called keep-change-flip. Keep the first fraction as it is. Change the divide sign to a multiply sign. Flip the second fraction upside down, so it becomes its reciprocal. Then multiply like you already know how.
Nina has 5/6 of a bag of rice. She pours it into cups that hold 5/12 of the bag each. Keep 5/6, change divide to multiply, flip 5/12 to 12/5. 5/6 x 12/5 = 60/30 = 2. She fills 2 cups.
Only flip the second fraction, the one right after the divide sign. If you flip the first fraction instead, or forget to flip at all, the answer will be wrong.
To divide a fraction by a fraction: keep the first fraction, change divide to multiply, and flip the second fraction upside down.
Watch it
Where it sits
This opens up
Nothing builds on it yet.
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.