Circumference = …………….`xx` diameter

Answer

To solve the problem, we need to determine what the circumference of a circle is in relation to its diameter.

### Step-by-Step Solution:

1. **Understand the Definitions**:
- The **circumference** of a circle is the distance around it.
- The **diameter** of a circle is the distance across it, passing through the center.

**Hint**: Remember that the circumference is like the perimeter for circles.

2. **Know the Formula**:
- The formula for the circumference (C) of a circle is given by:
\[ C = 2 \pi r \]
where \( r \) is the radius of the circle.

**Hint**: The radius is half of the diameter.

3. **Relate Radius to Diameter**:
- The diameter (D) of a circle is twice the radius:
\[ D = 2r \]
Therefore, we can express the radius in terms of diameter:
\[ r = \frac{D}{2} \]

**Hint**: Use the relationship between radius and diameter to transform the formula.

4. **Substitute Radius in the Circumference Formula**:
- Substitute \( r \) in the circumference formula:
\[ C = 2 \pi \left(\frac{D}{2}\right) \]
This simplifies to:
\[ C = \pi D \]

**Hint**: Simplifying the formula helps to see the relationship clearly.

5. **Final Conclusion**:
- From the equation \( C = \pi D \), we can conclude that the circumference is equal to \( \pi \) times the diameter.

**Hint**: The constant \( \pi \) is approximately 3.14 or can be expressed as \( \frac{22}{7} \).

### Final Answer:
Circumference = \( \pi \) × diameter.