Double Number Line Worksheets - Math Monks - Free Printable

Let's solve each problem step-by-step using double number lines, as instructed. A double number line helps visualize proportional relationships between two quantities.

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1) There are 20 chocolate bars in 4 boxes. Then, the number of chocolate bars in 12 boxes is:

Step 1: Find how many chocolate bars per box.
- 20 bars ÷ 4 boxes = 5 bars per box

Step 2: Multiply by 12 boxes.
- 5 bars/box × 12 boxes = 60 bars

✔ Answer: 60

Double Number Line:
```
Boxes: 4 → 8 → 12
Bars: 20→ 40→ 60
```

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2) It takes a chef 30 minutes to cook 2 dishes. How long will it take him to cook 10 dishes?

Step 1: Find time per dish.
- 30 minutes ÷ 2 dishes = 15 minutes per dish

Step 2: Multiply by 10 dishes.
- 15 × 10 = 150 minutes

✔ Answer: 150 minutes

Double Number Line:
```
Dishes: 2 → 4 → 6 → 8 → 10
Minutes: 30→ 60→ 90→120→150
```

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3) The ratio of boys to girls in a class is 5:3. If there are 30 boys, how many girls are there?

Step 1: Use the ratio 5:3 → for every 5 boys, 3 girls.

Step 2: Find multiplier:
- 30 boys ÷ 5 = 6 (so scale factor is 6)

Step 3: Multiply girls part:
- 3 × 6 = 18 girls

✔ Answer: 18

Double Number Line:
```
Boys: 5 → 10 → 15 → 20 → 25 → 30
Girls: 3 → 6 → 9 →12 →15 →18
```

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4) Olivia ran 1 mile in 10 minutes. At the same rate, how much time will it take her to run 4 miles?

Step 1: Rate is 10 minutes per mile

Step 2: For 4 miles:
- 10 × 4 = 40 minutes

✔ Answer: 40 minutes

Double Number Line:
```
Miles: 1 → 2 → 3 → 4
Minutes: 10→ 20→ 30→ 40
```

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5) If 3 apples cost 21 cents, how much would 12 apples cost?

Step 1: Cost per apple:
- 21 ÷ 3 = 7 cents per apple

Step 2: 12 apples:
- 7 × 12 = 84 cents

✔ Answer: 84 cents

Double Number Line:
```
Apples: 3 → 6 → 9 → 12
Cents: 21→ 42→ 63→ 84
```

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6) If 60% of an amount is $12, what is 100% of that amount?

Step 1: Let total amount be $x$.
So, 60% of x = 12
→ 0.60x = 12
→ x = 12 ÷ 0.60 = $20

✔ Answer: $20

Double Number Line:
```
Percentage: 60% → 100%
Amount ($): 12 → 20
```

(We can scale: 60% → 12, so 10% → 2, then 100% → 20)

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✔ Final Answers:

1) 60
2) 150 minutes
3) 18 girls
4) 40 minutes
5) 84 cents
6) $20

Let me know if you'd like visual drawings of the double number lines!