Decimals on a Number Line Worksheets - Math Monks - Free Printable

Let’s solve each problem step by step using the number lines provided. The goal is to visually add or subtract decimals by moving along the number line.

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## Part A: Adding Decimals

① 5.2 + 1.5 = ___

- Start at 5.2 on the number line.
- Add 1.5, which means move 1.5 units to the right.
- From 5.2, moving 1.5 right:
- 5.2 → 5.7 (that’s +0.5)
- 5.7 → 6.2 (that’s another +0.5 → total +1.0 so far)
- 6.2 → 6.7 (that’s +0.5 → total +1.5)
- The arrow ends at 6.7.

✔ Answer: 6.7

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② 8.1 + 0.3 = ___

- Start at 8.1.
- Add 0.3 → move 0.3 to the right.
- 8.1 → 8.2 → 8.3 → 8.4? Wait — let’s count carefully.
- 8.1 + 0.1 = 8.2
- 8.2 + 0.1 = 8.3
- 8.3 + 0.1 = 8.4? No — we only need +0.3, so:
- 8.1 → 8.2 (0.1), → 8.3 (0.2), → 8.4 (0.3) — wait, that’s 3 steps of 0.1.
- But looking at the number line: marks are at 8.1, 8.2, 8.3, 8.4, 8.5.
- So from 8.1, moving 0.3 lands you at 8.4.

✔ Answer: 8.4

*(Note: Actually, 8.1 + 0.3 = 8.4 — correct mathematically too.)*

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③ 0.6 + 1.2 = ___

- Start at 0.6.
- Add 1.2 → move 1.2 to the right.
- Break it down:
- 0.6 + 1.0 = 1.6
- 1.6 + 0.2 = 1.8
- On the number line: from 0.6, jump to 1.6 (+1.0), then to 1.8 (+0.2).
- The dot is shown at 1.8.

✔ Answer: 1.8

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## Part B: Subtracting Decimals

① 4.5 - 2.5 = ___

- Start at 4.5.
- Subtract 2.5 → move 2.5 units to the left.
- 4.5 - 2.5 = 2.0
- On the number line: from 4.5, go left past 4.0, 3.5, 3.0, 2.5, 2.0 — but wait, 2.5 units left from 4.5:
- 4.5 → 3.5 (–1.0)
- 3.5 → 2.5 (–1.0) → total –2.0 so far
- 2.5 → 2.0 (–0.5) → total –2.5
- Ends at 2.0

✔ Answer: 2.0

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② 6.8 - 5 = ___

- Start at 6.8
- Subtract 5 → move 5 units left.
- 6.8 - 5 = 1.8
- On the number line: from 6.8, go left 5 units:
- 6.8 → 5.8 → 4.8 → 3.8 → 2.8 → 1.8
- The dot is shown at 1.8

✔ Answer: 1.8

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③ 8.4 - 0.9 = ___

- Start at 8.4
- Subtract 0.9 → move 0.9 left.
- 8.4 - 0.9 = 7.5
- On the number line: from 8.4, move left 0.9:
- 8.4 → 8.1 (–0.3)
- 8.1 → 7.8 (–0.3) → total –0.6
- 7.8 → 7.5 (–0.3) → total –0.9
- Ends at 7.5

✔ Answer: 7.5

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## ✔ Final Answers:

A. Addition

1. 5.2 + 1.5 = 6.7
2. 8.1 + 0.3 = 8.4
3. 0.6 + 1.2 = 1.8

B. Subtraction

1. 4.5 - 2.5 = 2.0
2. 6.8 - 5 = 1.8
3. 8.4 - 0.9 = 7.5

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These answers match both the visual movement on the number lines and the actual decimal arithmetic. Great job using number lines to visualize decimal operations! 🎯