Illustrative Mathematics Grade 4, Unit 3: Extending Operations to Fractions
In this unit, your child adds and subtracts fractions and mixed numbers with like denominators, and multiplies a fraction by a whole number. They use line plots of measurements in halves, fourths, and eighths to ask and answer questions. It builds on last unit's equivalent fractions and leads into decimals and very large numbers.
By Robert “Bobby” BarnettMath teacher, parent, and founder of Bobby’s Math Club
What is my child learning in Unit 3?
- Decomposing fractions into sums, like 5/8 = 1/8 + 4/8, and adding and subtracting mixed numbers with like denominators. Learn more: Adding and subtracting fractions and mixed numbers
- Seeing 3 × 2/5 as 3 groups of 2/5, and solving story problems that multiply a fraction by a whole number. Learn more: Multiplying a fraction by a whole number
- Reading line plots of measurements in eighths of an inch, and adding or subtracting the fractions to answer questions. Learn more: Charting measurements in halves, fourths, and eighths
Sample questions to try together
These are real questions from our 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
Which sum is equal to 4/5?
- 1/5 + 1/5 + 1/5
- 1/4 + 1/4 + 1/4 + 1/4
- 1/5 + 1/5 + 1/5 + 1/5
How you can help
- Measure five toy cars or spoons to the nearest eighth of an inch. Make a line plot together and ask your child the total length of the two shortest.
- Talk about a walk in quarter miles. If each lap of a block is 1/4 mile and you walk 6 laps, ask how far that is, as 6/4 and 1 2/4 miles.
- Ask about party leftovers. If 1 2/6 pans of brownies are left and your family eats 5/6 of a pan, ask your child how much remains.
Where kids can get stuck
- Subtracting 1 2/6 − 5/6 by taking 2/6 from 5/6, without trading the whole for sixths.
- Plotting 3/4 and 6/8 as two different points, so the line plot shows two piles instead of one.
- Multiplying both the numerator and denominator by the whole number, so 3 × 2/5 becomes 6/15.
Practice makes perfect
Bobby's Math Club has practice problems that adapt to your child’s level, each with a detailed explanation and an easy-to-follow video, so your child can build confidence in these skills one step at a time.
Words your child will hear
- unit fraction
- A fraction with 1 as its numerator, like 1/4 or 1/8.
- decompose
- To break a number or fraction into parts, like 3/4 = 1/4 + 1/4 + 1/4.
- mixed number
- A whole number and a fraction together, like 2 1/4.
- like denominators
- Denominators that are the same, as in 3/8 and 5/8.
- line plot
- A number line with an X above it for each measurement in a set of data.
- product
- The answer to a multiplication problem.
Want to help your child master adding and multiplying fractions?
In Bobby's Math Club, your child practices these skills at just the right level, with a hint when they need one, a clear explanation after every question, and kid-friendly videos. Unlimited practice is free.
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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.
Which math standards does Illustrative Mathematics Grade 4 Unit 3 cover?
Illustrative Mathematics Grade 4 Unit 3 covers these math standards. Each one links to what it means, sample questions, and teaching strategies.
For teachers: Unit names and order vary between editions and districts, so your school’s own materials have the exact sequence. Learn how Bobby's Math Club can help your students grow.