A focused Grade 3 learning session for Adding and Subtracting Within 1000 using visual models, worked examples, strategy guidance, and a short mastery check.
Student goal: I can add and subtract within 1,000 and explain my strategy.
Adding and Subtracting Within 1000 means using place value, operations, and equations to reason accurately with numbers.
Question: Which number does this place-value chart show?
Why it works: Reading the chart: \(3\) hundreds is \(300\), \(5\) tens is \(50\), \(4\) ones is \(4\). Total: \(300+50+4=354\).
Answer: \(354\)
Question: The bar model above shows \(378\) broken into hundreds, tens, and ones. What is \(378+215\)?
Answer: \(593\)
Question: Using the place-value chart, what is \(642-215\)?
| Subtraction Problem | ||
|---|---|---|
| Hundreds | Tens | Ones |
| \(6\) | \(4\) | \(2\) |
| \(-\) | \(-\) | \(-\) |
| \(2\) | \(1\) | \(5\) |
Answer: \(427\)
Question: A school library has \(456\) books. The librarian buys \(244\) more books. How many books are in the library now?
Why it works: Add: \(456+244=700\). Ones: \(6+4=10\) (write \(0\), carry \(1\)). Tens: \(5+4+1=10\) (write \(0\), carry \(1\)). Hundreds: \(4+2+1=7\).
Answer: \(700\)
Adding and Subtracting Within 1000 becomes easier when students connect the question to a model, use clear steps, and explain why the answer fits.
Understand the model before choosing the operation.
Use scratch paper. The explanation matters more than simply seeing whether the choice is correct.
What is \(486+237\)?
Answer C: \(723\)
Add the ones (\(6+7=13\), write \(3\), carry \(1\)), tens (\(8+3+1=12\), write \(2\), carry \(1\)), hundreds (\(4+2+1=7\)). Answer: \(723\).
Which number does this place-value chart show?
Answer A: \(354\)
Reading the chart: \(3\) hundreds is \(300\), \(5\) tens is \(50\), \(4\) ones is \(4\). Total: \(300+50+4=354\).
\(245+318=?\)
Answer A: \(563\)
Add ones: \(5+8=13\) (write \(3\), carry \(1\)). Add tens: \(4+1+1=6\). Add hundreds: \(2+3=5\). Answer: \(563\).
Ben has \(127\) stickers. He gets \(234\) more stickers. How many stickers does Ben have now?
Answer D: \(361\)
Add: \(127+234=361\). Ones: \(7+4=11\) (write \(1\), carry \(1\)). Tens: \(2+3+1=6\). Hundreds: \(1+2=3\).
What is \(542-218\)?
Answer D: \(324\)
Subtract: ones (\(2-8\) requires regrouping, so \(12-8=4\)), tens (\(3-1=2\)), hundreds (\(5-2=3\)). Answer: \(324\).
Using the place-value chart, what is \(367+215\)?
Answer D: \(582\)
Ones: \(7+5=12\) (write \(2\), carry \(1\)). Tens: \(6+1+1=8\). Hundreds: \(3+2=5\). Answer: \(582\).
\(308+175=?\)
Answer A: \(483\)
Ones: \(8+5=13\) (write \(3\), carry \(1\)). Tens: \(0+7+1=8\). Hundreds: \(3+1=4\). Answer: \(483\).
A school library has \(456\) books. The librarian buys \(244\) more books. How many books are in the library now?
Answer A: \(700\)
Add: \(456+244=700\). Ones: \(6+4=10\) (write \(0\), carry \(1\)). Tens: \(5+4+1=10\) (write \(0\), carry \(1\)). Hundreds: \(4+2+1=7\).
What is \(635-241\)?
Answer A: \(394\)
Ones: \(5-1=4\). Tens: \(3-4\) requires regrouping, so \(13-4=9\). Hundreds: \(5-2=3\). Answer: \(394\).
The bar model above shows \(378\) broken into hundreds, tens, and ones. What is \(378+215\)?
Answer A: \(593\)
\(378+215\): ones \(8+5=13\) (write \(3\), carry \(1\)), tens \(7+1+1=9\), hundreds \(3+2=5\). Answer: \(593\).
\(524+312=?\)
Answer A: \(836\)
Ones: \(4+2=6\). Tens: \(2+1=3\). Hundreds: \(5+3=8\). Answer: \(836\).
