Reveal Math Grade 2, Unit 5: Two-Digit Addition
In this unit, your child adds two-digit numbers. They break numbers into tens and ones, regroup ten ones as a new ten, add up to four numbers at once, and add 10 or 100 in their heads. They also explain why their strategies work. It builds on place value to 1,000 and leads straight into two-digit subtraction.
By Robert “Bobby” BarnettMath teacher, parent, and founder of Bobby’s Math Club
What is my child learning in Unit 5?
- Adding two-digit numbers within 100, like 47 + 38, by adding tens, then ones, and regrouping when there are 10 or more ones. Learn more about adding within 100: Adding within 100 · Learn more about subtracting within 100
- Adding up to four two-digit numbers, like 23 + 45 + 17 + 30, by finding pairs that are easy to add first. Learn more: Adding up to four two-digit numbers
- Adding 10 or 100 to a number in their heads, like knowing that 10 more than 293 is 303. Learn more: Adding or taking away 10 or 100 mentally
- Explaining why their addition strategy works, using tens and ones, such as why 47 + 38 is the same as 50 + 35. 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 points in a board game or card game with two-digit scores, like 47 and 38. Ask your child to add the tens first, then the ones.
- Add up four numbers, such as 23, 45, 17, and 30. Ask which two are easy to add first, like 23 and 17 making 40.
- Ask 'What's 10 more?' on a walk or ride, using house numbers. Make it tricky now and then with numbers like 293.
Where kids can get stuck
- Writing all of 15 in the ones place instead of regrouping it as 1 ten and 5 ones.
- Leaving out one number when adding four, so the total comes out too small.
- Answering 2103 for 10 more than 293, instead of seeing that 10 tens make a new hundred, so it is 303.
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
- addend
- One of the numbers you add. In 8 + 5 = 13, the addends are 8 and 5.
- sum
- The answer when you add. In 8 + 5 = 13, the sum is 13.
- regroup
- To trade 10 ones for 1 ten, or 10 tens for 1 hundred, and back again.
- tens
- Groups of ten. The 4 in 45 means 4 tens, or 40.
- ones
- Single units. The 5 in 45 means 5 ones.
- make a ten
- A strategy that fills a ten first, so 9 + 5 becomes 10 + 4.
- strategy
- A plan or way to solve a problem.
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 Reveal Math Grade 2 Unit 5 cover?
Reveal Math Grade 2 Unit 5 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.