3rd Grade · Operations & Algebraic Thinking
3.OA.A.4: Find the missing number, like 7 × ? = 56 or ? ÷ 3 = 6
3.OA.A.4 is a 3rd 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
Determine the unknown whole number in a multiplication or division equation relating three whole numbers. For example, determine the unknown number that makes the equation true in each of the equations 8 x ? = 48, 5 = _ ÷ 3, 6 x 6 = ?.
In plain words
Find the missing number, like 7 × ? = 56 or ? ÷ 3 = 6.
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 the missing number? ? × 2 = 18
- 16
- 9
- 36
Where students can get stuck
- Multiplying the two numbers showing, so 7 x ? = 56 gets the answer 392, because the blank is usually the answer.
- Getting stuck on an equation written backward, like 40 = ? x 5, and thinking it must be wrong.
- Dividing when the unknown comes first in a division problem, so ? ÷ 3 = 6 gets 2 instead of 18.
Effective teaching strategies
- Write one fact in different forms, such as 7 × ? = 56, ? × 7 = 56, and 56 = 7 × ?, and have students show that they all ask the same question.
- Ask students to say the equation as a question, such as 7 times what number makes 56, before they solve it.
- Have students check an answer by putting it back in the equation, which shows why ? ÷ 3 = 6 needs 18 and not 2.
Units that teach this standard
Find where 3.OA.A.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
Eureka Math
Eureka Math²
Everyday Mathematics
Go Math!
i-Ready Classroom Mathematics
Illustrative Mathematics
Math Expressions
Don’t see your curriculum? Contact Bobby and we’ll see if we can help!
Share it with families
Families can read Finding the missing number, like 7 x ? = 56 for a plain-language look at this skill, with 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.