Eureka Math² Grade 2, Module 2: Addition and Subtraction Within 100
In this unit, your child adds and subtracts within 100. They break numbers into tens and ones, regroup when needed, add up to four numbers, and add or take away 10 in their head. They explain why their strategies work and use them in word problems. Measuring length comes next, where these skills help add and compare lengths.
By Robert “Bobby” BarnettMath teacher, parent, and founder of Bobby’s Math Club
What is my child learning in Module 2?
- Solving one- and two-step word problems within 100, choosing to add or subtract from a tape diagram. Learn more: One- and two-step story problems within 100
- Adding and subtracting two-digit numbers by tens and ones, regrouping a ten when needed. Learn more about adding within 100: Adding within 100 · Learn more about subtracting within 100
- Adding three or four two-digit numbers in a smart order, such as adding 27 + 13 first to make 40. Learn more: Adding up to four two-digit numbers
- Adding or subtracting 10 in their head, like 10 more than 68 or 10 less than 103. Learn more: Adding or taking away 10 or 100 mentally
- Explaining why a strategy works, using drawings of tens and ones or a number line. 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 80 minus 20?
- 50
- 60
- 70
How you can help
- Add up the points from a board game, and ask your child to find two numbers that make a friendly ten before adding the rest.
- Name a number on a walk or ride and ask for 10 more and 10 less, then ask which digit changed.
- Ask "How do you know?" after your child solves 74 − 38, and let them show it with a sketch of tens and ones.
Where kids can get stuck
- Saying 10 more than 95 is 905, getting stuck when the tens digit is 9.
- Subtracting 4 − 8 as 8 − 4 in the ones place, so 74 − 38 becomes 44.
- Grouping numbers into a friendly ten and then forgetting one of the four addends.
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.
- tens
- Groups of 10. In 47, the 4 means 4 tens, or 40.
- ones
- Single units. In 47, the 7 means 7 ones.
- addend
- Each number being added. In 5 + 3 = 8, the addends are 5 and 3.
- sum
- The answer when you add numbers together.
- difference
- The answer when you subtract; it also tells how much more one amount is.
- tape diagram
- A drawing of bars, like strips of tape, that shows the parts and the whole of a story.
- strategy
- A way of solving a problem, like making a ten or counting on.
Ready to build your child’s confidence with two-digit adding and subtracting?
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.
Join the club
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 Eureka Math² Grade 2 Module 2 cover?
Eureka Math² Grade 2 Module 2 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.