Real-world fraction multiplication
Solve real-world problems involving multiplication of fractions and mixed numbers, using visual fraction models or equations
What a learner can do afterwards
- Solve: 'A recipe needs 2 1/3 cups of flour; you want to make 1 1/2 batches. How much flour?'
- Draw a fraction model to represent and solve a multiplication word problem
- Check the reasonableness of a fraction product in context using estimation
1 · Read
You already know how to multiply fractions and mixed numbers. Now you will use that skill on real problems: recipes, materials, distances. The trick is spotting when a problem is really asking you to multiply. Watch for the word 'of', like '2/3 of a recipe' or 'half of a board'.
A recipe needs 2 1/3 cups of flour for one batch. You want to make 1 1/2 batches. First, change both mixed numbers to fractions: 2 1/3 = 7/3, and 1 1/2 = 3/2. Multiply: 7/3 x 3/2 = 21/6 = 3 1/2. Check it with an estimate: 2 1/3 is close to 2, and 1 1/2 is close to 1.5, so 2 x 1.5 = 3. Your exact answer, 3 1/2, is close to that estimate, so it makes sense. You need 3 1/2 cups of flour.
Before you multiply, round the mixed numbers to the nearest whole number and multiply those. If your exact answer is close to that rounded guess, you probably did it right.
To solve a real fraction problem, turn mixed numbers into fractions, multiply, then check your answer with a quick estimate.
2 · Watch
Take it off screen
Where it sits
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
16 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.