Adding Subtracting Within 1 000
Part of the Math for Young Minds curriculum — designed for neurodivergent students, grounded in real-world examples.
📋 Session plan (for teachers)
Session 4 — Adding & subtracting within 1,000
Grade 2 · Math for Young Minds Total time: ~22 minutes Common Core: 2.NBT.B.7 Today's idea: Big numbers add and subtract the same way as small ones — one place at a time.
What students will be able to do
By the end of this session, the student can:
- Add and subtract numbers within 1,000.
- Regroup at the tens and hundreds places when needed.
- Line up numbers carefully by place value.
Materials
- Base-10 blocks per pair (hundreds flats, tens rods, ones cubes)
- Place-value mat
- Worksheet (one per student)
- Pencil
Substitution: If you don't have base-10 blocks, draw them. A square = 100, a stick = 10, a dot = 1. Kids can sketch right on the place-value mat.
New words
| Word | Meaning we use in class |
|---|---|
| column addition | Stacking numbers by place value to add or subtract. |
Heads-up — common confusions
- Some kids will not line up the columns. Hundreds under hundreds, tens under tens, ones under ones — every time.
- When both ones and tens need regrouping, kids often regroup once and forget the second.
- After regrouping tens, the hundreds column has a new "+1" to add in. It's easy to miss.
Plan
1 · Hello & today's idea — 2 min
"At the store, prices and totals get big. Today we'll add and subtract numbers all the way up to 1,000."
Hold up a hundreds flat, a tens rod, and a ones cube.
"100. 10. 1. Same blocks you know — we just use more of them today."
2 · Hands-on explore — 6 min
Hand each pair their blocks and a place-value mat.
Problem 1 (together): "Build 234 on your mat. Hundreds column, tens column, ones column."
Walk around. Check that hundreds are under hundreds.
"Now add 158. Put 1 more hundred, 5 more tens, 8 more ones on the mat."
Pause. Point to the ones column.
"4 ones plus 8 ones is 12 ones. That's too many for the ones column. What do we do?"
Listen. Guide them: trade 10 ones for 1 ten. Move it to the tens column.
"Now count: how many hundreds? how many tens? how many ones?"
Answer: 392.
3 · Connect to the math — 4 min
Write on the board, lined up carefully:
1
2 3 4
+ 1 5 8
-------
3 9 2
"This is column addition. We stack numbers by place value. Ones under ones. Tens under tens. Hundreds under hundreds."
Point to the little 1 on top.
"When ones make more than 9, we carry 1 ten up to the tens column. Same trade you just did with blocks."
"Subtraction works the same way — but if the top is too small, we borrow from the next column."
4 · Practice with support — 8 min
Pass out the worksheet. Students work in pairs. Blocks stay out for anyone who wants them.
Problem 2 (solo): 506 − 273. Remind them: the top ones is 6, the bottom ones is 3 — that part is easy. But 0 tens minus 7 tens? Borrow from the hundreds. → 233
Problem 3 (solo): 489 + 367. Two regroupings! Ones make 16 — carry a ten. Tens (with the carry) make 15 — carry a hundred. → 856
Problem 4 (stretch): A library has 645 books. They donate 178. How many are left? → 467
Circulate. Watch for:
- Are the columns lined up?
- After regrouping tens, did they add the carry to the hundreds?
- On problem 3, did they regroup twice?
If a pair is stuck, say: "Build it with blocks first. Then write it."
5 · What we did + Try at home — 2 min
"Today you added and subtracted big numbers using column addition. Line up the places. Regroup when you need to."
Hand out the take-home note:
"Find two 3-digit numbers around your home — page counts in two books, miles on two trips, house numbers on your block. Add them or subtract them with a grown-up."
Observation rubric — what to notice in this session
Use this during the session, not as a test. One observation per student is plenty.
| Where the student is | What you'd see |
|---|---|
| Developing | Needs help lining up columns. Forgets to regroup, or regroups only once when two are needed. |
| Using | Stacks numbers by place value. Regroups at ones and tens correctly. Gets problems 2 and 3 right. |
| Extending | Solves the library word problem without help. Explains the regrouping out loud, in their own words. |
No fail state. "Developing" today is "using" next week.
What's next (Session 5)
Building on this, Session 5 — Money: coins and making change uses the same addition and subtraction — but now with real coins and real prices. Same math, something kids already think about every day.
✏️ Worksheet (for students)
Math for Young Minds · Grade 2
Session 4 — Adding & subtracting within 1,000
[ Hello ] → [ Explore ] → [ Connect ] → [ Practice ← we are here ] → [ Try at home ]
Today's big idea
Stack big numbers by place value. Add or subtract one column at a time — ones, then tens, then hundreds.
If a column has too many, regroup to the next column.
Example we did together
We added 145 + 128 using base-10 blocks and column addition:
hundreds | tens | ones
1 | 4 | 5
+ | |
1 | 2 | 8
─────────────────────
ones: 5 + 8 = 13 → write 3, carry 1 ten
tens: 1 + 4 + 2 = 7
huns: 1 + 1 = 2
Answer: 2 7 3 → 273
Line up the columns. Always start with the ones.
Problem 1 — together
Add 234 + 158. Stack them by place value.
Use the box to draw base-10 blocks (flats, rods, cubes) and show your work:
┌─────────────────────────────────────────────────────────┐
│ hundreds │ tens │ ones │
│ │ │ │
│ 2 3 4 │
│ + 1 5 8 │
│ ───────────────────────── │
│ │
│ │
│ │
└─────────────────────────────────────────────────────────┘
Answer: 234 + 158 = ______
Problem 2 — on your own
Subtract 506 − 273. You'll need to regroup!
Hint: the ones are fine, but the tens column needs help. Borrow from the hundreds.
┌─────────────────────────────────────────────────────────┐
│ hundreds │ tens │ ones │
│ │
│ 5 0 6 │
│ − 2 7 3 │
│ ───────────────────────── │
│ │
│ │
│ │
└─────────────────────────────────────────────────────────┘
Answer: 506 − 273 = ______
Problem 3 — on your own
Add 489 + 367. Two regroupings this time!
Watch out: ones make more than 10, AND tens make more than 10.
┌─────────────────────────────────────────────────────────┐
│ hundreds │ tens │ ones │
│ │
│ 4 8 9 │
│ + 3 6 7 │
│ ───────────────────────── │
│ │
│ │
│ │
└─────────────────────────────────────────────────────────┘
Answer: 489 + 367 = ______
Problem 4 — stretch
A library has 645 books. They donate 178 of them.
How many books are left?
Set it up as column subtraction. Show your regrouping!
┌─────────────────────────────────────────────────────────┐
│ hundreds │ tens │ ones │
│ │
│ 6 4 5 │
│ − 1 7 8 │
│ ───────────────────────── │
│ │
│ │
│ │
└─────────────────────────────────────────────────────────┘
Books left: ______
Check yourself: 178 + your answer should give 645.
Today's words
| Word | What it means |
|---|---|
| column addition | Stacking numbers by place value to add or subtract |
Try at home tonight (1 minute)
Find two 3-digit numbers around your home. Add them or subtract them with a grown-up. Use column addition — line up the ones, tens, and hundreds!
Ideas to find your numbers:
- Page totals of two books on the shelf
- Miles driven on two trips (check the car!)
- Calorie counts on two snack packages
- House numbers on your block
- Channel numbers on the TV
- Prices on two things at the store
____ ____ ____
+ ____ ____ ____
─────────────────
____ ____ ____
Show a grown-up tomorrow morning.
🏠 Family guide (for parents)
Math for Young Minds · Grade 2 · Session 4
A note for grown-ups: today we added and subtracted with bigger numbers
What your child did today
In class today, we worked on adding and subtracting numbers up to 1,000.
We used base-10 blocks — hundreds flats, tens rods, and ones cubes — on a place-value mat. Stacking blocks by place value helps kids see what the numbers mean before they write anything down.
Then we practiced column addition: stacking numbers so ones line up with ones, tens with tens, and hundreds with hundreds. When a column got too full, we regrouped — trading 10 ones for a ten, or 10 tens for a hundred.
We tried problems like 234 + 158, 506 − 273, and 489 + 367. The last one needed regrouping twice.
Why this matters
Three-digit math is where place value really starts to pay off. If kids understand that the "3" in 234 means three tens, regrouping isn't a mystery — it's just trading. We're not after speed yet. We're after the click: oh, that's why we line them up. Speed comes later, on its own.
🏠 Try this tonight (1 minute)
Find two 3-digit numbers somewhere around your home. Add them, or subtract the smaller from the larger, with your child.
Easy places to look:
| Where | What to grab |
|---|---|
| Two books | Total pages of each |
| The car | Miles from two recent trips |
| Snack packages | Calorie counts on the back |
| Out the window | House numbers on your block |
A short script:
- "Let's stack them — ones under ones, tens under tens, hundreds under hundreds."
- "Add this column first. More than 9? We carry one over."
- "Does the answer feel about right?"
If they get stuck, that's fine. Slow down. Draw little circles for ones, lines for tens, squares for hundreds.
Words your child is learning
- Column addition — stacking numbers by place value to add or subtract
If your child says…
"This is easy." Great. Hand them a harder one — something like
489 + 367where they have to regroup twice. Ask them to talk you through it.
"This is hard." Also great. Hard means their brain is doing real work. Slow down and use objects — pennies for ones, dimes for tens, dollar bills for hundreds. The blocks at school help for a reason.
"I don't want to." That's okay. Try one number from the world instead of a worksheet — the page count of the book they're reading, the number on the front door. One problem is enough.
What's next
In our next session, we move to money — coins and making change. We'll use the same adding and subtracting, but with something kids already think about: coins, bills, and what's left after you pay.
Thanks for taking a minute tonight. These small kitchen-table moments are where math lives.
— Math for Young Minds
🔑 Cheat sheet (visual)
🔑 Add & Subtract by Place Value
Picture 1 — Stack by place value
H T O
2 3 4
+ 1 5 8
───────
3 9 2
hundreds │ tens │ ones
▢▢ │ ▭▭▭ │ ▫▫▫▫
▢ │ ▭▭▭▭▭│ ▫▫▫▫▫▫▫▫
This stacking is called column addition.
Picture 2 — Regroup once (subtract)
4 10
5 0¹⁄ 0¹⁄ 6 ← borrow from hundreds, then tens
− 2 7 3
─────────────
2 3 3
506
− 273
─────
233 ✨
Picture 3 — Regroup TWICE (add)
¹ ¹
4 8 9
+ 3 6 7
─────────
8 5 6
ones: 9 + 7 = 16 → write 6, carry 1
tens: 1+8 + 6 = 15 → write 5, carry 1
hund: 1+4 + 3 = 8 → write 8
How to line it up
┌──── ones line up with ones
│
H T O
6 4 5
− 1 7 8
────────
4 6 7
│ │ │
│ │ └── ones column
│ └───── tens column
└──────── hundreds column
When to regroup?
| ✅ Regroup when... | ❌ No regroup when... |
|---|---|
8 + 7 = 15 (more than 9) |
4 + 3 = 7 (fits in one digit) |
0 − 3 (top is smaller) |
6 − 3 (top is bigger) |
| carry the 1 to next column | just write the digit |
Try this in your head
📚 Library has 645 books.
📦 They donate 178.
➤ 645 − 178 = ____
Answer:
467
🏠 Take home: Find two 3-digit numbers around your home (book pages, house numbers, trip miles). Add or subtract them with a grown-up.