Subtraction - Crossing 10 (1) | Worksheets - Primary Stars Education - Free Printable

Let's solve the subtraction problems shown in the image, focusing on "Subtraction – Crossing 10 (1)", which involves breaking numbers into parts to make subtraction easier when crossing the tens boundary (e.g., going from 12 to 10 or below).

We'll go through each part step-by-step, explaining how to use number bonds, part-part-whole models, ten-frames, and number lines.

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🔹 Understanding the Concept:

When subtracting a number that crosses 10 (like 12 - 3), we break it into two steps:
1. Subtract to reach 10.
2. Then subtract the rest from 10.

This is called bridging through 10.

For example:
> 12 - 3 = (12 - 2) - 1 = 10 - 1 = 9

We use:
- Ten-frame diagrams to show counters.
- Number bonds (like 12 = 10 + 2).
- Number lines to visualize jumps.

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## ✔ Part a: 12 - 3

Given:
```
12 - 3
```

Break 3 into 2 and 1 because:
- 12 - 2 = 10 (to get to 10)
- Then 10 - 1 = 9

So:
- First box: `12 - 2 = 10`
- Second box: `10 - 1 = 9`

✔ Final answer: 12 - 3 = 9

Now, draw the missing counters in the ten-frame:
- Start with 12 counters (10 in full frame, 2 extra).
- Remove 3: cross out 2 (from the extra), then 1 from the full ten-frame.
- So, after removing 2 from the extra, you have 10 left; then remove 1 more → 9 remain.

On the number line:
- Start at 12
- Jump back 2 to 10
- Jump back 1 to 9

➡️ Number line shows: 12 → 10 → 9

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## ✔ Part b: 15 - 7

Break 7 into 5 and 2:
- 15 - 5 = 10
- 10 - 2 = 8

So:
- First box: `15 - 5 = 10`
- Second box: `10 - 2 = 8`

✔ Final answer: 15 - 7 = 8

Draw counters:
- 15 counters: full ten-frame (10), plus 5 more.
- Remove 5 from the extra → now only 10 left.
- Remove 2 more from the ten-frame → 8 remain.

Number line:
- Start at 15
- Jump back 5 to 10
- Jump back 2 to 8

➡️ 15 → 10 → 8

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## ✔ Part c: 14 - 9

Break 9 into 4 and 5:
- 14 - 4 = 10
- 10 - 5 = 5

So:
- First box: `14 - 4 = 10`
- Second box: `10 - 5 = 5`

✔ Final answer: 14 - 9 = 5

Draw counters:
- 14 counters: full ten-frame (10), plus 4 more.
- Remove 4 from the extra → now only 10 left.
- Remove 5 from the ten-frame → 5 remain.

Number line:
- Start at 14
- Jump back 4 to 10
- Jump back 5 to 5

➡️ 14 → 10 → 5

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📌 Summary of Answers:

| Problem | Step 1 | Step 2 | Answer |
|--------|--------|--------|--------|
| a) 12 - 3 | 12 - 2 = 10 | 10 - 1 = 9 | 9 |
| b) 15 - 7 | 15 - 5 = 10 | 10 - 2 = 8 | 8 |
| c) 14 - 9 | 14 - 4 = 10 | 10 - 5 = 5 | 5 |

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✔ How to Fill In the Worksheet:

#### For each section:
1. Fill in the yellow box: The amount you subtract first to get to 10.
- a) 2
- b) 5
- c) 4

2. Fill in the pink box: The remaining amount to subtract from 10.
- a) 1
- b) 2
- c) 5

3. Complete the equations:
- a) 12 - 2 = 10, 10 - 1 = 9
- b) 15 - 5 = 10, 10 - 2 = 8
- c) 14 - 4 = 10, 10 - 5 = 5

4. Draw counters:
- Use red dots for initial count.
- Cross out the ones being removed (yellow X).
- Show final count.

5. Number line:
- Draw arrows showing the two jumps: one to 10, then to final answer.

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💡 Teaching Tip:

This method helps children understand place value and mental math strategies by breaking subtraction into manageable steps.

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