4th Grade · Operations & Algebraic Thinking
4.OA.B.4: Find factors and multiples up to 100, and spot prime numbers
4.OA.B.4 is a 4th grade Common Core math standard in Operations & Algebraic Thinking. 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
Find all factor pairs for a whole number in the range 1-100. Recognize that a whole number is a multiple of each of its factors. Determine whether a given whole number in the range 1-100 is a multiple of a given one-digit number. Determine whether a given whole number in the range 1-100 is prime or composite.
In plain words
Find factors and multiples up to 100, and spot prime numbers.
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 6
4 × 9 = 36. Which sentence is true?
- 4 is a multiple of 36.
- 36 is a multiple of 4, but not of 9.
- 36 is a multiple of both 4 and 9.
Where students can get stuck
Find factors and multiples up to 100.
- Missing factor pairs, such as finding 2 × 18 and 3 × 12 for 36 but not 4 × 9 or 6 × 6.
- Mixing up factors and multiples, saying 12 is a factor of 3 when they mean it is a multiple of 3.
- Leaving out 1 and the number itself, so the factors of 15 are listed as only 3 and 5.
Spot prime numbers.
- Thinking every odd number is prime, so they call 9, 15, or 21 prime even though 9 = 3 × 3.
- Calling 2 composite because it is even, when it is the only even prime number.
- Calling 91 prime because no times-table fact comes to mind, even though 91 = 7 × 13.
Effective teaching strategies
- List factor pairs of 36 in order by testing 1, 2, 3, 4, 5, and 6, and stop at 6 × 6, so students find 4 × 9 and do not skip it.
- Have students say both words about one equation, such as 3 × 4 = 12, where 3 and 4 are factors and 12 is a multiple of each.
- Ask students to hunt for a factor other than 1 and itself in 9, 15, and 21, so they see odd numbers can be composite, then test 2, 4, and 6 to find the one even prime.
Units that teach this standard
Find where 4.OA.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 Math
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
Each skill has its own guide for families, with a plain-language look at the skill, three questions to try together, and ideas for helping at home.
Help every student practice problem solving 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.