Find the missing number in each proportion on this printable math worksheet.

To solve the missing proportions, we need to use the property of proportions, which states that in a proportion \(a : b = c : d\), the cross-products are equal: \(a \cdot d = b \cdot c\). Let's solve each problem step by step.

Left Column

1. 120 : 80 = 90 : ?
- Cross-multiply: \(120 \cdot ? = 80 \cdot 90\)
- \(120 \cdot ? = 7200\)
- \(? = \frac{7200}{120} = 60\)
- Answer: 60

2. 150 : 300 = ? : 120
- Cross-multiply: \(150 \cdot 120 = 300 \cdot ?\)
- \(18000 = 300 \cdot ?\)
- \(? = \frac{18000}{300} = 60\)
- Answer: 60

3. 25 : ? = 75 : 12
- Cross-multiply: \(25 \cdot 12 = 75 \cdot ?\)
- \(300 = 75 \cdot ?\)
- \(? = \frac{300}{75} = 4\)
- Answer: 4

4. 12 : 125 = ? : 250
- Cross-multiply: \(12 \cdot 250 = 125 \cdot ?\)
- \(3000 = 125 \cdot ?\)
- \(? = \frac{3000}{125} = 24\)
- Answer: 24

5. 45 : 80 = 90 : ?
- Cross-multiply: \(45 \cdot ? = 80 \cdot 90\)
- \(45 \cdot ? = 7200\)
- \(? = \frac{7200}{45} = 160\)
- Answer: 160

6. 20 : ? = 70 : 63
- Cross-multiply: \(20 \cdot 63 = 70 \cdot ?\)
- \(1260 = 70 \cdot ?\)
- \(? = \frac{1260}{70} = 18\)
- Answer: 18

7. 15 : ? = 45 : 285
- Cross-multiply: \(15 \cdot 285 = 45 \cdot ?\)
- \(4275 = 45 \cdot ?\)
- \(? = \frac{4275}{45} = 95\)
- Answer: 95

8. 120 : ? = 60 : 175
- Cross-multiply: \(120 \cdot 175 = 60 \cdot ?\)
- \(21000 = 60 \cdot ?\)
- \(? = \frac{21000}{60} = 350\)
- Answer: 350

9. 144 : 180 = 12 : ?
- Cross-multiply: \(144 \cdot ? = 180 \cdot 12\)
- \(144 \cdot ? = 2160\)
- \(? = \frac{2160}{144} = 15\)
- Answer: 15

10. 380 : 100 = ? : 75
- Cross-multiply: \(380 \cdot 75 = 100 \cdot ?\)
- \(28500 = 100 \cdot ?\)
- \(? = \frac{28500}{100} = 285\)
- Answer: 285

Right Column

1. 20 : 15 = 40 : ?
- Cross-multiply: \(20 \cdot ? = 15 \cdot 40\)
- \(20 \cdot ? = 600\)
- \(? = \frac{600}{20} = 30\)
- Answer: 30

2. 196 : 182 = ? : 130
- Cross-multiply: \(196 \cdot 130 = 182 \cdot ?\)
- \(25480 = 182 \cdot ?\)
- \(? = \frac{25480}{182} = 140\)
- Answer: 140

3. 15 : 90 = 13 : ?
- Cross-multiply: \(15 \cdot ? = 90 \cdot 13\)
- \(15 \cdot ? = 1170\)
- \(? = \frac{1170}{15} = 78\)
- Answer: 78

4. 45 : ? = 18 : 40
- Cross-multiply: \(45 \cdot 40 = 18 \cdot ?\)
- \(1800 = 18 \cdot ?\)
- \(? = \frac{1800}{18} = 100\)
- Answer: 100

5. 24 : 100 = 60 : ?
- Cross-multiply: \(24 \cdot ? = 100 \cdot 60\)
- \(24 \cdot ? = 6000\)
- \(? = \frac{6000}{24} = 250\)
- Answer: 250

6. 150 : 750 = ? : 35
- Cross-multiply: \(150 \cdot 35 = 750 \cdot ?\)
- \(5250 = 750 \cdot ?\)
- \(? = \frac{5250}{750} = 7\)
- Answer: 7

7. 25 : 80 = 5 : ?
- Cross-multiply: \(25 \cdot ? = 80 \cdot 5\)
- \(25 \cdot ? = 400\)
- \(? = \frac{400}{25} = 16\)
- Answer: 16

8. 160 : ? = 128 : 144
- Cross-multiply: \(160 \cdot 144 = 128 \cdot ?\)
- \(23040 = 128 \cdot ?\)
- \(? = \frac{23040}{128} = 180\)
- Answer: 180

9. 35 : 55 = 70 : ?
- Cross-multiply: \(35 \cdot ? = 55 \cdot 70\)
- \(35 \cdot ? = 3850\)
- \(? = \frac{3850}{35} = 110\)
- Answer: 110

10. 240 : 360 = ? : 120
- Cross-multiply: \(240 \cdot 120 = 360 \cdot ?\)
- \(28800 = 360 \cdot ?\)
- \(? = \frac{28800}{360} = 80\)
- Answer: 80

Final Answers

```
Left Column:
60, 60, 4, 24, 160, 18, 95, 350, 15, 285

Right Column:
30, 140, 78, 100, 250, 7, 16, 180, 110, 80
```

So, the final answer is:
\[
\boxed{60, 60, 4, 24, 160, 18, 95, 350, 15, 285, 30, 140, 78, 100, 250, 7, 16, 180, 110, 80}
\]