i-Ready Classroom Mathematics Grade 2, Unit 4: Addition and Subtraction Within 1000
In this unit, your child adds and subtracts within 1,000. They break numbers into hundreds, tens, and ones, regroup when a place has too many or too few, and add or take away 10 or 100 in their head. They explain why each strategy works. Next comes measurement, time, and money, where these skills get put to use.
By Robert “Bobby” BarnettMath teacher, parent, and founder of Bobby’s Math Club
What is my child learning in Unit 4?
- Adding and subtracting three-digit numbers by place value, with drawings, number lines, and a written method. Learn more about adding within 1,000: Adding within 1,000 · Learn more about subtracting within 1,000
- Adding or subtracting 10 or 100 mentally from numbers between 100 and 900, noticing which digit changes. Learn more: Adding or taking away 10 or 100 mentally
- Explaining why their strategies work, such as why 10 tens can be traded for 1 hundred. 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
A toy store had 450 toy cars and sold 120 of them. How many toy cars are left?
- 320
- 570
- 330
How you can help
- Add the page counts of two books, like 340 and 285, and let your child explain how they handled the tens.
- Say a number like 760 on a walk or ride, and ask for 100 less and 10 more, then let your child quiz you.
- Ask your child to show 512 − 247 with quick drawings of hundreds, tens, and ones, and to explain each trade.
Where kids can get stuck
- Taking the smaller digit from the larger in each column, so 512 − 247 becomes 335.
- Saying 100 more than 718 is 728, changing the tens digit instead of the hundreds.
- Forgetting the regrouped hundred, so 470 + 250 comes out as 620 instead of 720.
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
- hundreds
- Groups of 100. In 706, the 7 means 7 hundreds, or 700.
- regroup
- Trading 10 ones for 1 ten, or 1 ten for 10 ones, to add or subtract.
- place value
- The value a digit has because of its spot in a number: ones, tens, or hundreds.
- mentally
- In your head, without writing it down or using objects.
- strategy
- A way of solving a problem, like making a ten or counting on.
- sum
- The answer when you add numbers together.
- difference
- The answer when you subtract; it also tells how much more one amount is.
Ready to build your child’s confidence with three-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 i-Ready Classroom Mathematics Grade 2 Unit 4 cover?
i-Ready Classroom Mathematics 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.