"3-Digit Subtraction Base-Ten Worksheet - Check for Understanding"

Let's solve each subtraction problem using base-ten blocks as a model, just like the worksheet asks. Base-ten blocks represent numbers using:

- Hundred blocks (100s): big squares
- Tens rods (10s): long sticks
- Units (ones): small squares

We’ll go through each problem step by step.

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Problem 1: 241 - 128

#### Step 1: Represent 241 with base-ten blocks
- 2 hundreds → 2 hundred blocks
- 4 tens → 4 ten rods
- 1 one → 1 unit block

So:
✔ 2 hundreds, 4 tens, 1 one

Now subtract 128:
- 1 hundred, 2 tens, 8 ones

But we don’t have enough ones to subtract 8 (only 1). So we need to regroup.

#### Step 2: Regroup
- Take 1 ten rod and exchange it for 10 ones.
- Now we have:
- 2 hundreds
- 3 tens (since we used 1 ten)
- 11 ones (1 original + 10 from regrouping)

Now subtract:
- 1 hundred → 2 - 1 = 1 hundred
- 2 tens → 3 - 2 = 1 ten
- 8 ones → 11 - 8 = 3 ones

✔ Final answer: 113

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Problem 2: 317 - 233

#### Step 1: Represent 317
- 3 hundreds
- 1 ten
- 7 ones

Subtract 233:
- 2 hundreds, 3 tens, 3 ones

But we only have 1 ten — not enough to subtract 3 tens. So we need to regroup.

#### Step 2: Regroup
- Take 1 hundred and exchange it for 10 tens.
- Now:
- 2 hundreds (3 - 1)
- 11 tens (1 + 10)
- 7 ones

Now subtract:
- Hundreds: 2 - 2 = 0
- Tens: 11 - 3 = 8
- Ones: 7 - 3 = 4

✔ Final answer: 84

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Problem 3: 450 - 307

#### Step 1: Represent 450
- 4 hundreds
- 5 tens
- 0 ones

Subtract 307:
- 3 hundreds, 0 tens, 7 ones

We have no ones, but we need to subtract 7 ones → so we must regroup.

#### Step 2: Regroup
- Take 1 ten rod and exchange it for 10 ones.
- Now:
- 4 hundreds
- 4 tens (5 - 1)
- 10 ones

Now subtract:
- Hundreds: 4 - 3 = 1
- Tens: 4 - 0 = 4
- Ones: 10 - 7 = 3

✔ Final answer: 143

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Problem 4: 213 - 45

#### Step 1: Represent 213
- 2 hundreds
- 1 ten
- 3 ones

Subtract 45:
- 4 tens, 5 ones

We only have 1 ten and 3 ones — not enough to subtract 4 tens or 5 ones. So we need to regroup twice.

#### Step 2: Regroup
- Take 1 hundred → exchange for 10 tens → now we have:
- 1 hundred
- 11 tens (1 + 10)
- 3 ones

But still not enough ones → take 1 ten and exchange for 10 ones:
- Now:
- 1 hundred
- 10 tens (11 - 1)
- 13 ones (3 + 10)

Now subtract:
- Hundreds: 1 - 0 = 1
- Tens: 10 - 4 = 6
- Ones: 13 - 5 = 8

✔ Final answer: 168

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✔ Final Answers:

1. 241 - 128 = 113
2. 317 - 233 = 84
3. 450 - 307 = 143
4. 213 - 45 = 168

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How to Show Thinking on the Worksheet:

For each problem, you would cross out or remove the blocks you are subtracting, showing the regrouping steps. For example:

- In Problem 1: Cross out 1 hundred, 2 tens, and 8 ones, but show that you broke a ten into 10 ones first.
- Use the grid boxes to visually show the remaining blocks.

You can draw:
- Remaining hundreds in the big squares
- Remaining tens in the rods
- Remaining ones in the small squares

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✔ The green checkmark indicates the student has completed the task correctly. Your answers match the expected outcomes!

Let me know if you'd like a visual representation of any step!