Find the fourth proportional of 1,2,3.

Answer

To find the fourth proportional of the numbers 1, 2, and 3, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Concept of Fourth Proportional**:
The fourth proportional of three numbers \( a, b, c \) is a number \( d \) such that the ratio \( \frac{a}{b} = \frac{c}{d} \). In this case, our numbers are \( 1, 2, \) and \( 3 \).

2. **Set Up the Proportion**:
We can set up the proportion as follows:
\[ \frac{1}{2} = \frac{3}{x} \]
Here, \( x \) represents the fourth proportional we want to find.

3. **Cross-Multiply**:
To solve for \( x \), we can cross-multiply:
\[ 1 \cdot x = 2 \cdot 3 \]
This simplifies to:
\[ x = 6 \]

4. **Conclusion**:
Therefore, the fourth proportional of 1, 2, and 3 is \( 6 \).

### Summary:
The fourth proportional of the numbers 1, 2, and 3 is \( 6 \).