Reveal Math Grade 2, Unit 7: Three-Digit Addition
In this unit, your child adds three-digit numbers within 1,000. They add hundreds, tens, and ones, regroup ones and tens when needed, add 10 or 100 in their heads, and use drawings to explain why their method works. It builds on two-digit subtraction and leads into three-digit subtraction next.
By Robert “Bobby” BarnettMath teacher, parent, and founder of Bobby’s Math Club
What is my child learning in Unit 7?
- Adding three-digit numbers, like 256 + 178, by adding hundreds, tens, and ones and regrouping when a place has 10 or more. Learn more about adding within 1,000: Adding within 1,000 · Learn more about subtracting within 1,000
- Adding 10 or 100 to numbers between 100 and 900 in their heads, like knowing 100 more than 678 is 778. Learn more: Adding or taking away 10 or 100 mentally
- Using drawings of hundreds, tens, and ones to explain why regrouping in addition works. 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 two three-digit numbers from a book, a box, or a sign, such as 256 + 178. Let your child add the hundreds first, then the tens, then the ones.
- Play '100 more' on a walk or ride: you say 678, and your child says 778. Then try 10 more, and switch roles.
- Ask your child to draw a quick picture of 256 using squares for hundreds, lines for tens, and dots for ones, then add 178 the same way.
Where kids can get stuck
- Writing each place's total right into the answer, so 256 + 178 becomes 31214 instead of 434.
- Saying 688 for 100 more than 678, changing the tens digit instead of the hundreds digit.
- Saying 'I carried the one' without knowing the one stands for 1 ten or 1 hundred.
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. The 3 in 352 means 3 hundreds, or 300.
- regroup
- To trade 10 ones for 1 ten, or 10 tens for 1 hundred, and back again.
- compose
- To put parts together to make a bigger unit, like 10 tens making 1 hundred.
- sum
- The answer when you add. In 8 + 5 = 13, the sum is 13.
- addend
- One of the numbers you add. In 8 + 5 = 13, the addends are 8 and 5.
- place value
- What a digit is worth because of where it sits. In 352, the 5 means 50.
- digit
- One of the symbols 0 to 9 used to write numbers. 352 has three digits.
Want to help your child master three-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 Reveal Math Grade 2 Unit 7 cover?
Reveal Math Grade 2 Unit 7 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.