A circle of radius r cm has a diameter of length

Options

A. r cm
B. 2r cm
C. 4r cm
D. `r/2c m`

Answer

To solve the question, we need to understand the relationship between the radius and the diameter of a circle.

### Step-by-Step Solution:

1. **Understand the Definitions**:
- The radius (r) of a circle is the distance from the center of the circle to any point on its circumference.
- The diameter (d) of a circle is the distance across the circle through its center, which is twice the length of the radius.

2. **Formula for Diameter**:
- The formula to find the diameter of a circle is:
\[ d = 2 \times r \]
- Here, \( r \) is the radius.

3. **Substituting the Value**:
- Given that the radius of the circle is \( r \) cm, we can substitute this value into the formula:
\[ d = 2 \times r = 2r \text{ cm} \]

4. **Choosing the Correct Option**:
- Now, we need to compare our result \( 2r \) cm with the provided options:
- a) r cm
- b) 2r cm
- c) 4r cm
- d) r/2 cm
- The correct answer is clearly option b) \( 2r \) cm.

### Final Answer:
The diameter of the circle is \( 2r \) cm, which corresponds to option b.