enVision Mathematics Grade 2, Topic 6: Fluently Subtract Within 100
In this unit, your child subtracts within 100 with a written method, regrouping a ten as 10 ones when there are not enough ones to take away. They check subtraction with addition and explain why each step works. This follows the mental strategies from earlier and leads into a stretch of mixed story problems, where choosing the right operation matters.
By Robert “Bobby” BarnettMath teacher, parent, and founder of Bobby’s Math Club
What is my child learning in Topic 6?
- Subtracting two-digit numbers on paper, trading a ten for 10 ones when needed, as in 82 − 56 = 26. Learn more about adding within 100: Adding within 100 · Learn more about subtracting within 100
- Explaining why trading a ten works, and checking a subtraction answer by adding it back to the number taken away. Learn more about explaining why addition strategies work: Explaining why addition strategies work · Learn more about explaining why subtraction strategies work
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 your child to work out change in their head when something costs 37 cents and they pay with 50 cents, then check by adding back.
- Ask "Do we have enough ones?" each time your child subtracts, such as 71 − 45, and let them show the trade with drawings of tens and ones.
- Check answers together: if 90 − 34 is 56, does 56 + 34 make 90? Let your child be the one who checks your answers, too.
Where kids can get stuck
- Taking the smaller digit from the larger one, so 82 − 56 becomes 34 instead of 26.
- Trading a ten for ones but forgetting to cross out that ten, so the answer is 10 too big.
- Checking subtraction by adding the wrong two numbers, then deciding a correct answer is wrong.
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
- regroup
- Trading 10 ones for 1 ten, or 1 ten for 10 ones, to add or subtract.
- difference
- The answer when you subtract; it also tells how much more one amount is.
- tens
- Groups of 10. In 47, the 4 means 4 tens, or 40.
- ones
- Single units. In 47, the 7 means 7 ones.
- place value
- The value a digit has because of its spot in a number: ones, tens, or hundreds.
- check
- To make sure an answer is right, such as adding back after subtracting.
- strategy
- A way of solving a problem, like making a ten or counting on.
Ready to build your child’s confidence with 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 enVision Mathematics Grade 2 Topic 6 cover?
enVision Mathematics Grade 2 Topic 6 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.