Math Expressions Grade 2, Unit 4: Subtract 2-Digit Numbers
In this unit, your child subtracts two-digit numbers. They learn to ungroup a ten into ten ones when there are not enough ones, check subtraction with addition, and explain why their method works. They also solve story problems that call for subtracting. It builds on adding within 200 and on measuring, and leads into time, graphs, and more word problems.
By Robert “Bobby” BarnettMath teacher, parent, and founder of Bobby’s Math Club
What is my child learning in Unit 4?
- Subtracting within 100, like 82 - 56, by ungrouping a ten into ten ones and checking the answer with addition. Learn more about adding within 100: Adding within 100 · Learn more about subtracting within 100
- Explaining why ungrouping works, showing with a drawing that 82 is still 82 when written as 7 tens and 12 ones. Learn more about explaining why addition strategies work: Explaining why addition strategies work · Learn more about explaining why subtraction strategies work
- Solving subtraction story problems, including 'how many more' and 'how many fewer,' and writing an equation for each. Learn more: One- and two-step story problems within 100
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
What is 10 + 25 + 5?
- 30
- 40
- 45
How you can help
- Ask how many pages are left in a book with 82 pages after reading 56. Let your child show you how they ungrouped a ten to find out.
- Check a subtraction answer with addition: if 82 - 56 = 26, ask your child to add 26 + 56 and see if it makes 82.
- Tell a 'how many fewer' story at snack time: 'You have 24 crackers. I have 9. How many fewer crackers do I have?'
Where kids can get stuck
- Taking the smaller digit from the larger in each column, writing 34 for 82 - 56 instead of ungrouping a ten.
- Ungrouping a ten but forgetting to cross it out, so the tens digit stays one too big.
- Adding whenever a story says 'more,' even in 'how many more' questions that call for subtracting.
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
- difference
- The answer when you subtract. In 13 - 5 = 8, the difference is 8.
- ungroup
- To break 1 ten into 10 ones so you can subtract.
- tens
- Groups of ten. The 4 in 45 means 4 tens, or 40.
- ones
- Single units. The 5 in 45 means 5 ones.
- equation
- A number sentence with an equal sign, like 13 - 5 = 8.
- fewer
- Less in number. 9 is 15 fewer than 24.
- subtract
- To take away, or to find how far apart two numbers are.
Want to help your child master two-digit subtraction?
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 2 Unit 4 cover?
Math Expressions Grade 2 Unit 4 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.