We now look at solving perimeter problems at a slightly advanced level, that also includes some concepts from other mathematics topics.

Calculate the perimeter of a rectangular field with dimensions 75 m x 20 m.
Perimeter = 2(l + b)
= 2(75 + 20)
= 2 x 95
= 190 m

A wire fence needs to be erected around the sides of a farm with dimensions 20.3 m x 9.2 m.
a) Find the length of the fencing required
b) Calculate the cost of the fencing wire at $10 per metre
Perimeter of the farm = 2(l + b)
= 2(20.3 + 9.2)
= 2 x 29.5
= 59 m
Cost of wire fence = 59 x 10 = $590

The perimeter of a rectangular backyard is 34 m. If the yard is 6 m wide, find its length.
Perimeter = 2(l + b)
34 = 2(l + 6)
l + 6 = 17
l = 17 – 6
= 11 m
So the length of the backyard is 11 metres.

A square has the same perimeter as an equilateral triangle. If the triangle has sides of length 8 cm, what is the side length of the square.
Given equilateral triangle with side = 8 cm,
its perimeter = 8 + 8 + 8
= 24 cms
4s = 24
s = 24 ÷ 4
= 6 cm
So the side length of the square is 6 cm
 The length of a rectangle is twice its width. Find the dimensions of the rectangle if the perimeter is 36 cm
When length l is twice its width, we can express the length l = 2b.
So perimeter = 2(l + b) = 36
2(2b + b) = 36
3b = 18
b = 6
So the breadth of the rectangle is 6 cm, and its length is 12 cm (being twice its width). 
A swimming pool has a 2 metre wide path around its edge. The outer dimensions of the path are 35 x 20 m. Find
a) the dimensions of the pool
b) the perimeter of the pool
Since there is a 2 metre wide path around the swimming pool, the actual dimensions of the pool will be 2 m less than the outer length and breadth on both sides.
So length of the pool = 35 – 2 – 2 = 31 m
and breadth of the pool = 20 – 2 – 2 = 16 m
Therefore the dimensions of the pool are 31 x 16 m
Perimeter of the pool = 2(31 + 16)
= 2 x 47
= 94 m

A school ground is 110 m long and 30 m wide. How far, in kilometres, will an athlete run by completing 20 laps of the track?
Perimeter of the school ground = 2(110 + 30)
= 2 x 140
= 280 m
Doing 20 laps around the track = 280 x 20
= 5600 m
= 5.6 km (1 km = 1000 m)