For finding radius, we need to have one of the three parameters: volume, total surface area or circumference of the cylinder.

- If we have circumference, then we can find the radius by a simple formula as circumference = $2 \pi r$. And, when we get the radius, we can easily find the diameter by doubling it.
- If we have the total surface and height, then we can find the radius by the formula, total surface area = $2 \pi r (h + r)$.
- If we have volume, then we can find the diameter of the cylinder by a simple calculation. We know that the volume of a cylinder is $\pi r^2 h$. So, with volume, we also need height to find the diameter.

Now we will see an example in which we will find the diameter of a cylinder.

**Example:**

If the volume of a cylinder is 33 inch, and height is 7 inch, then find the diameter of the cylinder.

**Solution:**

Volume of a cylinder = $\pi r^2 h$

So, according to the question.

$33$ = $\frac{22}{7}$$ \times r^2 \times 7$

$r^2$ = $\frac{22}{7}$$ \times $$\frac{7}{33}$

$r^2$ = $\frac{2}{3}$

r = $\sqrt{\frac{2}{3}}$ inch.

Diameter = 2$\sqrt{\frac{2}{3}}$ inch..