Largo : x
Ancho : y
Si el largo excede el ancho en 20m :
<img src="https://tex.z-dn.net/?f=x%3Dy%2B20" />
<img src="https://tex.z-dn.net/?f=P_%7Boriginal%7D%20%3D2x%2B2y%0A%0AP_%7Boriginal%7D%20%3D2%28y%2B20%29%2B2y%3D2y%2B20%2B2y%3D4y%2B20%0A%0AP_%7Boriginal%7D%20%3D4y%2B20%0A%0A" />
Si el ancho se reduce en su tercera parte y su largo a su mitad : - Nuevo largo : x / 2 - Nuevo ancho : y / 3
<img src="https://tex.z-dn.net/?f=P_%7Bnuevo%7D%20%3D2%2A%28x%2F2%29%2B2%2A%28y%2F3%29%3D%202x%2F2%2B2y%2F3%3Dx%2B2x%2F3%0A%0AP_%7Bnuevo%7D%20%3Dx%2B2x%2F3" />
Si el perímetro nuevo es 5 / 9 del original :
<img src="https://tex.z-dn.net/?f=P_%7Bnuevo%7D%3D5%2F9%2AP_%7Boriginal%7D%0A%0Ax%2B2x%2F3%3D5%2F9%2A%284y%2B20%29" />
Podemos sustituir<img src="https://tex.z-dn.net/?f=y%3Dx-20" /> :
<img src="https://tex.z-dn.net/?f=x%2B2x%2F3%3D5%2F9%2A%284%28x-20%29%2B20%29%0A%0Ax%2B2x%2F3%3D5%2F9%2A%284x-80%2B20%29%0A%0Ax%2B2x%2F3%3D5%2F9%2A%284x-60%29%0A%0Ax%2B2x%2F3%3D20x%2F9-5%2A60%2F9%29%0A%0Ax%2B2x%2F3%3D20x%2F9-300%2F9%29%0A%0Ax%2B2x%2F3%3D20x%2F9-100%2F3%29%0A%0A3x%2F3%2B2x%2F3%3D20x%2F9-100%2F3%0A%0A5x%2F3-20x%2F9%3D-100%2F3%0A%0A15x%2F9-20x%2F9%3D-100%2F3%0A%0A-5x%2F9%3D-100%2F%0A%0A5x%2F9%3D100%0A%0A5x%3D900%0A%0Ax%3D900%2F5%0A%0Ax%3D180" />
Si x = 180 :
<img src="https://tex.z-dn.net/?f=y%3Dx-20%0A%0Ay%3D180-20%0A%0Ay%3D160" />
Entonces :
El largo es x = 180m y el ancho y = 160m.