Multiplying fractions in real life, like recipes
In 5th grade, children learn to solve real-world problems that multiply fractions and mixed numbers, like scaling a recipe or finding the area of a garden with fractional sides.
By Robert “Bobby” BarnettMath teacher, parent, and founder of Bobby’s Math Club
Try these with your child
These are real questions from our 5th grade practice. Tap the speaker to hear one read aloud, or the light bulb for a hint, and talk about the answer together.
Question 1 of 3
A baby giraffe is 6 feet tall. Its mother is 2 1/2 times as tall as the baby. How tall is the mother?
- 8 1/2 feet
- 12 feet
- 15 feet
Why this matters
For your child, spotting multiplication inside a real situation is harder than doing the calculation, and it is the part that will matter most later. Scaling a recipe by 1 1/2, finding the area of a garden bed, or taking half of what is left are everyday versions. In 6th and 7th grade the same thinking powers ratio, rate, and percent problems, which appear throughout middle school.
Where kids can get stuck
- Multiplying whole numbers and fractions separately, so 2 1/2 × 1 1/2 becomes 2 1/4 instead of 3 3/4.
- Adding when the problem says "half of," so half of 3/4 of a pizza becomes 1 1/4 instead of 3/8.
- Skipping the check for a sensible answer, so they accept that half of 6 1/2 yards of fabric is more than 6 yards.
How you can help
- Scale a family recipe up or down. If pancakes need 1 1/4 cups of milk and you are making double, ask how much milk you need. Let your child measure out the 2 1/2 cups.
- Measure a rug, table, or garden bed with fractional lengths, like 4 1/2 feet by 3 feet, and ask your child to find its area. Talk about why the answer, 13 1/2 square feet, makes sense.
- When there are leftovers, ask a "fraction of a fraction" question: if 2/3 of a pan of brownies is left and your child eats 1/4 of what is left, how much of the whole pan did they eat?
Bobby's Math Club offers free practice that grows with your child.
Questions parents ask
Why is my child learning to multiply fractions with real-world problems?
Knowing the steps for multiplying fractions is only useful if your child recognizes when a situation calls for it. Real problems, like scaling a recipe or finding the area of a garden, help your child connect words like "of" and "times as much" to multiplication. Teachers also use these problems to build the habit of checking whether an answer is reasonable.
Why does my child turn mixed numbers into improper fractions?
Changing 2 1/2 into 5/2 makes multiplication straightforward, because your child can multiply tops and bottoms directly. Multiplying the whole number parts and fraction parts separately gives the wrong answer. Some children also use an area model, multiplying each part and adding them, which works when done carefully and shows why the simple shortcut fails.
How can I tell if my child really understands fraction word problems?
Ask your child to explain why they chose to multiply and to estimate the answer before calculating. If they can say "I need 1 1/2 batches, so it should be a bit more than one batch's worth," they understand the situation. Getting the arithmetic right without being able to explain it suggests the idea is still settling.
Make learning math fun
Bobby's Math Club turns 5th grade math practice into something fun to do together.
- Unlimited practice, completely free
- A few minutes a day, at just the right level
- Hints when they are stuck, and a celebration when it clicks
Written by Robert “Bobby” Barnett
Bobby is an award-winning math teacher, the author of Meet Every Learner’s Needs, and the father of two elementary-school math learners. He uses Bobby’s Math Club with his own kids a few times every week. Learn more or contact Bobby.
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Join the clubNote for teachers: This skill is covered by Common Core math standard 5.NF.B.6: “Solve real world problems involving multiplication of fractions and mixed numbers, e.g., by using visual fraction models or equations to represent the problem.” Learn how Bobby's Math Club can help your students grow. (Common Core 5.NF.6)