enVision Mathematics Grade 2, Topic 4: Fluently Add Within 100
In this unit, your child moves from mental strategies to adding within 100 with a written method, lining up tens and ones and regrouping when the ones make 10 or more. They add three and four numbers at once and explain why their method works. Next, the same tens-and-ones thinking turns around for subtraction.
By Robert “Bobby” BarnettMath teacher, parent, and founder of Bobby’s Math Club
What is my child learning in Topic 4?
- Adding two-digit numbers on paper, lining up the tens and ones and regrouping 10 ones as 1 ten when needed. Learn more about adding within 100: Adding within 100 · Learn more about subtracting within 100
- Adding up to four two-digit numbers, grouping friendly pairs first, such as 25 + 15 to make 40. Learn more: Adding up to four two-digit numbers
- Explaining why their adding method works, using drawings of tens and ones to show what the regrouped 1 really is. 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
- Add up three or four prices on a menu or receipt, and ask your child which pair to add first to make an easy ten.
- Have your child add the ages of everyone in the family, saying the ones and then the tens out loud as they go.
- Ask "What does that little 1 mean?" after your child regroups, and let them show it with a bundle of 10 sticks or straws.
Where kids can get stuck
- Writing all of 15 in the ones place instead of regrouping the ten, so 47 + 28 becomes 615.
- Skipping one of the numbers when adding four in a row, so the total comes out short.
- Saying "I carried the one" without knowing that the one is really a ten.
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.
- addend
- Each number being added. In 5 + 3 = 8, the addends are 5 and 3.
- sum
- The answer when you add numbers together.
- 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.
- strategy
- A way of solving a problem, like making a ten or counting on.
Want to help your child master two-digit addition?
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 4 cover?
enVision Mathematics Grade 2 Topic 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.