The ratio of radius and circumference of a circle is `:`

Options

A. `pi :1`
B. `1: pi `
C. `1: 2pi `
D. `2pi : 1`

Answer

To find the ratio of the radius to the circumference of a circle, we can follow these steps:

### Step-by-Step Solution:

1. **Define the Radius**:
Let the radius of the circle be denoted as \( r \).

2. **Calculate the Circumference**:
The formula for the circumference \( C \) of a circle is given by:
\[ C = 2\pi r \]

3. **Set Up the Ratio**:
We need to find the ratio of the radius \( r \) to the circumference \( C \). Therefore, we set up the ratio as:
\[ \text{Ratio} = \frac{r}{C} = \frac{r}{2\pi r} \]

4. **Simplify the Ratio**:
In the ratio \( \frac{r}{2\pi r} \), the \( r \) in the numerator and denominator cancels out (assuming \( r \neq 0 \)):
\[ \frac{r}{2\pi r} = \frac{1}{2\pi} \]

5. **Final Result**:
Thus, the ratio of the radius to the circumference of a circle is:
\[ \frac{1}{2\pi} \]