Find which of the are in proportion :
`18,9,10,5`

Answer

To determine if the numbers 18, 9, 10, and 5 are in proportion, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the pairs to compare**: We will compare the first pair (18 and 9) with the second pair (10 and 5).

2. **Calculate the ratio of the first pair**:
\[ \text{Ratio of } 18 \text{ and } 9 = \frac{9}{18} \]
Simplifying this gives:
\[ \frac{9}{18} = \frac{1}{2} \]

3. **Calculate the ratio of the second pair**:
\[ \text{Ratio of } 10 \text{ and } 5 = \frac{5}{10} \]
Simplifying this gives:
\[ \frac{5}{10} = \frac{1}{2} \]

4. **Compare the two ratios**:
We found that:
\[ \frac{9}{18} = \frac{1}{2} \quad \text{and} \quad \frac{5}{10} = \frac{1}{2} \]
Since both ratios are equal, we can conclude that the numbers are in proportion.

5. **Final conclusion**:
Therefore, we can state that the numbers 18, 9, 10, and 5 are in proportion.

### Final Answer:
The numbers 18, 9, 10, and 5 are in proportion.

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