Math Expressions Grade 2, Unit 2: Addition Within 200
In this unit, your child adds two-digit numbers and starts adding numbers up to 200. They learn what each digit in a three-digit number is worth, write numbers in expanded form, and regroup ten ones as a new ten. They also explain why their methods work. This builds on facts within 20 and comes before a unit on length and shapes.
By Robert “Bobby” BarnettMath teacher, parent, and founder of Bobby’s Math Club
What is my child learning in Unit 2?
- Seeing that 10 tens make 1 hundred, so a number like 135 is 1 hundred, 3 tens, and 5 ones. Learn more: Hundreds, tens, and ones in numbers like 706
- Reading and writing numbers to 200 in numerals, words, and expanded form, like 100 + 30 + 5. Learn more: Reading and writing numbers to 1,000
- Adding two-digit numbers within 100, like 47 + 38, by adding tens and ones and making a new ten. Learn more about adding within 100: Adding within 100 · Learn more about subtracting within 100
- Adding numbers with totals up to 200, like 86 + 75, and trading 10 tens for 1 hundred when needed. Learn more about adding within 1,000: Adding within 1,000 · Learn more about subtracting within 1,000
- Explaining with drawings of hundreds, tens, and ones why a new ten or hundred appears when adding. 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
How many hundreds are in 300?
- 3
- 30
- 300
How you can help
- Add the scores in a board game or card game, such as 86 and 75. Ask your child to add the tens first, then the ones, and to say when a new hundred appears.
- Read numbers you see on a walk, like 135 on a mailbox, and ask how many hundreds, tens, and ones it has.
- Bundle straws or craft sticks into groups of 10, then use them to show 47 + 38. Ask your child to point out when ten loose ones become a new ten.
Where kids can get stuck
- Forgetting the new ten, so 47 + 38 comes out as 75 instead of 85.
- Writing all of 11 in the ones place when the ones add up to more than 9.
- Writing expanded form as digits, such as 1 + 3 + 5 for 135.
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
- hundred
- Ten tens, or 100. The 7 in 706 means 7 hundreds.
- digit
- One of the symbols 0 to 9 used to write numbers. 352 has three digits.
- place value
- What a digit is worth because of where it sits. In 352, the 5 means 50.
- expanded form
- A number written as the sum of its parts, like 352 = 300 + 50 + 2.
- regroup
- To trade 10 ones for 1 ten, or 10 tens for 1 hundred, and back again.
- 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.
Ready to build your child’s confidence with adding to 200?
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 Math Expressions Grade 2 Unit 2 cover?
Math Expressions Grade 2 Unit 2 covers these math standards. Each one links to what it means, sample questions, and teaching strategies.
- 2.NBT.A.1: Understand that the three digits of a three-digit number represent amounts of hundreds, tens, and ones.
- 2.NBT.A.3: Read and write numbers to 1000 using base-ten numerals, number names, and expanded form.
- 2.NBT.B.5: Fluently add and subtract within 100.
- 2.NBT.B.7: Add and subtract within 1000.
- 2.NBT.B.9: Explain why addition and subtraction strategies work.
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.