Math Expressions Grade 1, Unit 3: Unknown Numbers in Addition and Subtraction
In this unit, your child solves story problems where the missing number can be anywhere: at the start, in the middle, or at the end. They write equations with a box or question mark for the unknown and figure out what it must be. This builds on last unit's strategies and leads into place value.
By Robert “Bobby” BarnettMath teacher, parent, and founder of Bobby’s Math Club
What is my child learning in Unit 3?
- Solving story problems within 20 where the start, the change, or the result is missing, using drawings and equations. Learn more: Adding and subtracting story problems within 20
- Finding the unknown in equations like ? + 6 = 14 or 12 - ? = 5 by using the relationship between the numbers. Learn more: Missing numbers, like 8 + ? = 11
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
I had some toy cars. My friend gave me 3 more cars. Now I have 8 cars in total. How many toy cars did I have at first?
- 3
- 5
- 8
How you can help
- Tell a missing-start story while folding towels: "I had some towels and folded 4 more. Now I have 10 folded. How many did I start with?"
- Write ? + 3 = 11 on a sticky note and ask your child to find the mystery number, then check it by adding.
- Ask your child to make up a story for 15 - ? = 9, then solve it together using drawings.
Where kids can get stuck
- Adding the two numbers they hear in a missing-start story, answering 14 instead of 4 when some birds and 5 more make 9.
- Using the total as the answer, instead of the missing number, when the unknown is in the middle.
- Treating the word more as a signal to add, even when the story asks how many more one child has.
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
- unknown
- The missing number in a problem, often shown as a box or a question mark.
- equation
- A number sentence with an equal sign, like 6 + 2 = 8.
- addend
- One of the numbers you add together, like 4 and 3 in 4 + 3.
- total
- How many there are altogether.
- number story
- A short story that ends with a math question to solve.
- how many more
- Words that ask for the difference between two amounts.
Want to help your child master story problems?
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 Math Expressions Grade 1 Unit 3 cover?
Math Expressions Grade 1 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.