The image above is a pentagon.

To compute the perimeter of a pentagon, one essential parameter is needed and this parameter is length of side (a).

The formula for calculating the perimeter of a pentagon:

P = 5a

Where;

P = Perimeter of the pentagon

a = length of side

Let’s solve an example;

Find the perimeter of a pentagon when the length of side (a) is 25 cm.

This implies that;

a = length of side = 25 cm

P = 5a

P = 5 x 25

P = 125

Therefore, the **perimeter of the pentagon** is **125 cm.**

**Calculating the length of side using the perimeter of the pentagon.**

a = ^{P} / _{5}

Where;

a = Length of side

P = Perimeter of the pentagon

Let’s solve an example;

Given that the area of the pentagon is 250 cm. Find the length of side?

This implies that;

P = Perimeter of the pentagon = 250 cm

a = ^{P} / _{5}

a = ^{250} / _{5}

a = 50

Therefore, the length of side (a) is 50 cm.