4th Grade · Number & Operations - Fractions
4.NF.B.4: Multiply a fraction by a whole number, like 2 × 3/4
4.NF.B.4 is a 4th grade Common Core math standard in Number & Operations - Fractions. Here’s what it really covers, and how you can help your students learn it.
By Robert “Bobby” BarnettMath teacher, parent, and founder of Bobby’s Math Club
The standard
Apply and extend previous understandings of multiplication to multiply a fraction by a whole number. a. Understand a fraction a/b as a multiple of 1/b. For example, use a visual fraction model to represent 5/4 as the product 5 × (1/4), recording the conclusion by the equation 5/4 = 5 × (1/4). b. Understand a multiple of a/b as a multiple of 1/b, and use this understanding to multiply a fraction by a whole number. For example, use a visual fraction model to express 3 × (2/5) as 6 × (1/5), recognizing this product as 6/5. c. Solve word problems involving multiplication of a fraction by a whole number, e.g., by using visual fraction models and equations to represent the problem. For example, if each person at a party will eat 3/8 of a pound of roast beef, and there will be 5 people at the party, how many pounds of roast beef will be needed? Between what two whole numbers does your answer lie?
In plain words
Multiply a fraction by a whole number, like 2 × 3/4.
Sample questions from student practice
These questions from Bobby's Math Club are the kinds of questions your students will see. You can try answering them to see what a student might see.
Question 1 of 3
What is 7 × 1/10?
- 7/70
- 1/70
- 7/10
Where students can get stuck
- Multiplying both the top and bottom by the whole number, so 2 × 3/4 becomes 6/8, which still equals 3/4.
- Getting the right fraction without a sense of its size, leaving 15/8 unrecognized as almost 2, or 1 7/8.
- Adding 5 and 3/8 in a word problem that calls for 5 groups of 3/8.
Effective teaching strategies
- Draw 2 × 3/4 as two jumps of 3/4 on a number line, so students see the total is 6/4 and only the numerator is multiplied.
- Ask students to write 5 × 3/8 as five copies of 3/8 added together and read the sum as 15 eighths.
- Give a story such as 5 bowls holding 3/8 cup of water each, have students write the equation, and rename the total, 15/8 cups, as 1 7/8 cups.
Units that teach this standard
Find where 4.NF.B.4 lands in the program you teach. Each unit has a guide written for families. Unit names and order vary between editions and districts, so your school’s own materials have the exact sequence.
Bridges in Mathematics
enVision Mathematics
Eureka Math²
Everyday Mathematics
i-Ready Classroom Mathematics
Illustrative Mathematics
Math Expressions
Reveal Math
Don’t see your curriculum? Contact Bobby and we’ll see if we can help!
Share it with families
Families can read Multiplying a fraction by a whole number for a plain-language look at this skill, with three questions to try together and ideas for helping at home.
Help every student practice fractions at home
In Bobby's Math Club, students practice 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 for every family.
See how it works for teachers
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.