Fence length:
28-18=10
30²-10²=800
Sqrt 800= 28.2843 = 28.3 metres
Area of lawn:
28.3x18=509.4 metres²
28.3x10=283/2=141.5 metres²
509.4+141.5=650.9 metres²
Amount of cans needed:
Each covers 100m² so 7 cans are needed
19.75x7=138.25
So total cost should be £138.25
