# What is the diameter of a circle with circumference 5?

Jun 26, 2018

$D = 1.6$

#### Explanation:

Using;

$C = 2 \pi r$

Where;

$C = \text{Circumference}$

$r = \text{Radius}$

Recall;

$D = 2 r$

$D = \text{Diameter}$

Therefore;

$r = \frac{D}{2}$

Substituting $r$ into the main equation..

$C = 2 \pi \left(\frac{D}{2}\right)$

$C = \cancel{2} \pi \left(\frac{D}{\cancel{2}}\right)$

$C = \pi D$

Making $D$ the subject;

$\frac{C}{D} = \frac{\pi D}{D}$

$\frac{C}{\pi} = \frac{\cancel{\pi} D}{\cancel{\pi}}$

$D = \frac{C}{\pi}$

When;

$C = 5$

$\pi = \frac{22}{7}$

$D = \frac{5}{\frac{22}{7}}$

$D = 5 \div \frac{22}{7}$

$D = 5 \times \frac{7}{22}$

$D = \frac{35}{22}$

$D = 1.59090$

$D = 1.6$